# Urine sediment examination veterinary ## Quick Answer - Urine sediment examination identifies cells, casts, crystals, and microorganisms to differentiate renal tubular damage, urinary tract inflammation, and crystalluria. - Perform the examination within 60 minutes of collection using a standardized centrifugation protocol and record all findings with a consistent reporting system. - Sediment findings require correlation with urine chemistry, physical properties, and clinical signs because many formed elements appear in healthy animals. ## At a Glance | Sediment Finding | Primary Clinical Association | Key Differentiating Feature | |---|---|---| | Red blood cells | Hemorrhage from the urinary tract, trauma, neoplasia, or coagulopathy | Dysmorphic cells suggest renal origin, while uniform cells suggest lower tract bleeding | | White blood cells | Bacterial cystitis, pyelonephritis, or interstitial nephritis | Degenerate neutrophils indicate active infection, mononuclear cells suggest chronic inflammation | | Epithelial cells | Transitional cell sloughing from bladder or renal pelvis, renal tubular cells indicate tubular damage | Renal tubular epithelial cells are larger than leukocytes with eccentric nuclei | | Hyaline casts | Concentrated urine, fever, exercise, or early renal disease | Transparent, low refractive index, easily missed under low light | | Granular casts | Tubular injury, nephrotoxicity, or advanced renal disease | Coarse granules indicate cellular breakdown within the tubule | | Calcium oxalate dihydrate crystals | Hypercalcemia, ethylene glycol toxicity, or dietary factors | Envelope-shaped crystals with distinct birefringence | | Struvite crystals | Urease-producing bacterial infection or concentrated alkaline urine | Coffin-lid morphology, dissolves with acetic acid | | Bacteria | Urinary tract infection, contamination during collection | Presence with pyuria and clinical signs supports infection | ## Clinical Context and Diagnostic Role Urine sediment examination is a core component of the complete urinalysis in veterinary medicine. The procedure provides direct visualization of formed elements that reflect the physiologic and pathologic state of the kidneys and lower urinary tract. Veterinarians use this test to differentiate renal tubular damage, urinary tract inflammation, and crystalluria, which often present with overlapping clinical signs such as hematuria, dysuria, and pollakiuria. The American Veterinary Medical Association emphasizes the importance of regular veterinary care for early detection of health problems in companion animals. Urinalysis is a routine component of preventive care examinations and is particularly valuable in older animals where renal disease prevalence increases. The American Animal Hospital Association includes urinalysis as part of comprehensive preventive care protocols for companion animals. The diagnostic value of urine sediment examination depends on proper collection, handling, and preparation. A poorly handled sample produces artifacts that can mislead the clinician and result in incorrect management decisions. The World Small Animal Veterinary Association provides global guidelines for clinical practice that emphasize standardized diagnostic procedures to ensure reliable results. Urine sediment examination is not a standalone diagnostic test. The results must be interpreted alongside urine specific gravity, dipstick chemistry, and the animal's clinical presentation. A finding of crystals without clinical signs may be incidental, while the same finding with hematuria and dysuria requires further investigation. ## Sample Collection and Handling ### Collection Methods The method of urine collection affects the interpretation of sediment findings. Free catch, catheterization, and cystocentesis each have distinct advantages and limitations. Free catch is the least invasive and is appropriate for routine screening, but it is prone to contamination from the distal urethra, genital tract, and perineum. Catheterization reduces contamination but can introduce bacteria into the bladder if performed improperly. Cystocentesis provides the most sterile sample and is preferred for bacterial culture, but it requires technical skill and carries a small risk of complications. The Merck Veterinary Manual describes the clinical approach to urinalysis and emphasizes that the collection method should be matched to the diagnostic question. For routine screening, free catch is acceptable. For suspected urinary tract infection, cystocentesis is the preferred method to avoid contamination. For monitoring of proteinuria, a free catch sample is often sufficient. ### Timing and Storage Urine sediment examination should be performed within 30 minutes of collection. Delayed examination leads to cellular degeneration, crystal formation, and bacterial overgrowth. If immediate examination is not possible, the sample should be refrigerated and examined within a few hours. Refrigeration slows bacterial growth and cellular degeneration but does not stop all changes. Crystals may form or dissolve with temperature changes, and casts may degrade. The sample should be collected in a clean, dry container. Preservatives are not routinely used for urine sediment examination because they can alter cellular morphology. The sample should be protected from light and excessive heat during transport. ### Sample Preparation Standardized preparation is essential for reproducible results. A 5 to 10 mL aliquot of well-mixed urine is centrifuged at a low speed for five minutes. The supernatant is decanted, and the sediment is resuspended in the remaining fluid. A drop of the resuspended sediment is placed on a slide and covered with a coverslip. The volume of urine used and the resuspension volume affect the concentration of formed elements. A standardized protocol ensures that results are comparable between samples and between laboratories. The use of a fixed volume of urine and a fixed resuspension volume allows semiquantitative reporting of findings. ### Staining Stains such as Sternheimer-Malbin or new methylene blue can be used to enhance the visibility of cellular detail. These stains help differentiate white blood cells from renal tubular epithelial cells and improve the identification of casts. Stains are not required for routine examination but are useful when cellular morphology is ambiguous. The stain is added to the sediment before examination. The amount of stain and the incubation time should be standardized to avoid overstaining, which can obscure cellular detail. Stained preparations should be examined promptly because the stain can cause cellular degeneration over time. ## Microscopic Examination Protocol ### Low-Power Examination The sediment is first examined under low power to identify casts and to assess the overall distribution of formed elements. Casts are present in low numbers and are best detected at low magnification. The entire coverslip should be scanned systematically to avoid missing focal findings. The low-power examination provides a semiquantitative assessment of the number of casts per low-power field. The presence of any casts is recorded, and the number is reported as few, moderate, or many. The type of cast is identified at higher magnification. ### High-Power Examination The sediment is then examined under high power to identify cells, crystals, and microorganisms. The number of each cell type is reported per high-power field. The morphology of the cells is assessed to determine the origin and the clinical significance. The high-power examination is used to identify the specific type of crystals present. Crystal morphology is described based on shape, color, and refractive index. The number of crystals is reported as few, moderate, or many. ### Reporting and Quantification The results of the sediment examination are reported in a standardized format. The number of cells is reported as the average number per high-power field. The number of casts is reported as the average number per low-power field. The presence of bacteria, crystals, and other formed elements is reported descriptively. The report should include the method of collection, the time between collection and examination, and the preparation protocol. This information is necessary for the clinician to interpret the results in the context of the sample quality. ## Formed Elements and Clinical Significance ### Red Blood Cells Red blood cells in urine sediment indicate hemorrhage somewhere in the urinary tract. The presence of red blood cells is called hematuria. The origin of the hemorrhage can be localized by the morphology of the cells and the presence of other findings. Dysmorphic red cells, which have irregular shapes and sizes, suggest a renal origin. These cells are damaged during passage through the renal tubules. Uniform red cells suggest a lower urinary tract origin, such as the bladder or urethra. Hematuria can be caused by trauma, urinary tract infection, urolithiasis, neoplasia, or coagulopathy. The presence of red cells with white cells and bacteria suggests infection. The presence of red cells with casts suggests renal disease. The presence of red cells without other findings may be due to trauma or neoplasia. The number of red cells is reported per high-power field. The presence of any red cells is clinically significant, but the degree of hematuria does not always correlate with the severity of the underlying disease. ### White Blood Cells White blood cells in urine sediment indicate inflammation of the urinary tract. The presence of white cells is called pyuria. The number of white cells is reported per high-power field. The morphology of the white cells provides information about the cause of the inflammation. Degenerate neutrophils, which have swollen and fragmented nuclei, suggest a bacterial infection. Nondegenerate neutrophils suggest inflammation without infection. Lymphocytes and macrophages may be present in chronic inflammation. Pyuria is commonly associated with bacterial urinary tract infection. The presence of white cells with bacteria and clinical signs supports the diagnosis of infection. Pyuria without bacteria may be due to sterile inflammation, urolithiasis, or neoplasia. The presence of white cells in the sediment should be interpreted with the urine culture results. A positive culture with pyuria confirms a urinary tract infection. A negative culture with pyuria may indicate a nonbacterial cause of inflammation. ### Epithelial Cells Epithelial cells in urine sediment can originate from the renal tubules, the transitional epithelium of the bladder and ureters, or the squamous epithelium of the distal urethra and genitalia. The type of epithelial cell provides information about the site of the pathology. Squamous epithelial cells are large, flat cells with a small nucleus. They are commonly present in free catch samples and are considered contamination from the distal urethra or genitalia. They are not clinically significant. Transitional epithelial cells are round to oval cells with a moderate amount of cytoplasm. They are present in small numbers in normal urine. An increased number of transitional cells suggests inflammation or neoplasia of the bladder or ureters. Renal tubular epithelial cells are the most clinically significant epithelial cells. They are larger than white cells and have a round nucleus. The presence of renal tubular cells indicates renal tubular damage. This can be caused by nephrotoxins, ischemia, or renal disease. The presence of renal tubular cells in the sediment is a specific indicator of renal tubular injury. The finding should be interpreted with the presence of casts and the clinical presentation. ### Casts Casts are cylindrical structures that form in the renal tubules. They are composed of protein, cells, or cellular debris. The presence of casts is called cylindruria. Casts are formed in the tubules and are a specific indicator of renal disease. Hyaline casts are composed of protein and are transparent. They are the most common type of cast and are present in concentrated urine, after exercise, or with proteinuria. They are not always clinically significant. Granular casts are composed of protein and cellular debris. They indicate renal tubular injury. The granules are the remnants of degenerated cells. The presence of granular casts suggests a more significant renal injury than hyaline casts. Cellular casts are composed of red cells, white cells, or epithelial cells. Red cell casts indicate glomerular hemorrhage. White cell casts indicate renal inflammation. Epithelial cell casts indicate renal tubular injury. The presence of casts in the sediment is a specific indicator of renal disease. The type of cast provides information about the location and the nature of the renal injury. ### Crystals Crystals are formed elements that precipitate from the urine. The presence of crystals is called crystalluria. Crystals can be normal or abnormal, depending on the type and the clinical context. Struvite crystals are composed of magnesium ammonium phosphate. They are coffin-shaped and colorless. They are commonly present in concentrated urine or in urine with a high pH. They are associated with urinary tract infections caused by urease-producing bacteria. Calcium oxalate crystals are composed of calcium oxalate. They are envelope-shaped and colorless. They are present in urine with a low pH. They are associated with hypercalcemia, ethylene glycol toxicity, or dietary factors. Uric acid crystals are composed of uric acid. They are diamond-shaped or rhomboid. They are present in urine with a low pH. They are associated with uric acid urolithiasis. Cystine crystals are hexagonal and colorless. They are present in urine with a low pH. They are associated with cystinuria, a genetic disorder. The presence of crystals is not always clinically significant. Crystals can be present in normal urine. The clinical significance is determined by the type of crystal, the number of crystals, and the clinical presentation. ### Microorganisms Bacteria in urine sediment indicate a urinary tract infection or contamination. The presence of bacteria is determined by the examination of the sediment under high power. The presence of bacteria with white cells and clinical signs supports a urinary tract infection. The presence of bacteria in the sediment should be confirmed by a urine culture. The culture identifies the specific bacteria and determines the antibiotic sensitivity. The culture is the definitive test for a urinary tract infection. Fungal elements, such as yeast, can be present in urine sediment. They are less common than bacteria. They are associated with fungal urinary tract infections, which are more common in immunocompromised animals. ### Parasites and Other Elements Parasites can be present in urine sediment. The most common is the parasite Capillaria, which is a nematode that infects the urinary tract. The eggs are present in the sediment. Other elements, such as sperm, can be present in the sediment. Sperm are present in intact male animals. They are not clinically significant. ## Clinical Interpretation and Differential Diagnosis ### Renal Tubular Damage Renal tubular damage is indicated by the presence of renal tubular epithelial cells, granular casts, and cellular casts. The presence of these elements indicates injury to the renal tubules. The injury can be caused by nephrotoxins, ischemia, or infection. The clinical presentation of renal tubular damage includes polyuria, polydipsia, and azotemia. The urine specific gravity is often low. The presence of tubular cells and casts in the sediment supports the diagnosis of renal tubular damage. The differentiation of renal tubular damage from other causes of renal disease is important for the management of the animal. The presence of tubular cells and casts is a specific indicator of tubular injury. The absence of these findings does not exclude renal disease. ### Urinary Tract Inflammation Urinary tract inflammation is indicated by the presence of white blood cells in the sediment. The inflammation can be caused by bacterial infection, urolithiasis, or neoplasia. The presence of white cells with bacteria and clinical signs supports a bacterial infection. The clinical presentation of urinary tract inflammation includes dysuria, pollakiuria, and hematuria. The urine is often cloudy and has a strong odor. The presence of white cells in the sediment is a specific indicator of inflammation. The differentiation of the cause of the inflammation is important for the management. The presence of bacteria in the sediment supports a bacterial infection. The presence of crystals supports urolithiasis. The presence of atypical cells supports neoplasia. ### Crystalluria Crystalluria is the presence of crystals in the urine. The crystals can be present in normal urine or can be associated with urolithiasis. The clinical significance is determined by the type of crystal, the number of crystals, and the clinical presentation. The presence of struvite crystals with a high urine pH and a bacterial infection supports a struvite urolithiasis. The presence of calcium oxalate crystals with a high urine calcium supports a calcium oxalate urolithiasis. The management of crystalluria depends on the type of crystal. The management of struvite urolithiasis includes the treatment of the bacterial infection and the acidification of the urine. The management of calcium oxalate urolithiasis includes the reduction of urine calcium and the increase of urine volume. ## Practical Implementation and Assessment ### Step-by-Step Procedure 1. Collect a fresh urine sample using the appropriate method for the clinical question. 2. Record the collection method, the time of collection, and the urine volume. 3. Centrifuge a fixed volume of urine at a standardized speed for a fixed time. 4. Decant the supernatant and resuspend the sediment in the remaining fluid. 5. Place a drop of the sediment onto a slide and apply a coverslip. 6. Examine the sediment under low power to identify casts. 7. Examine the sediment under high power to identify cells, crystals, and bacteria. 8. Report the findings in a standardized format. ### Records and Measurements The following records should be maintained for each urine sediment examination: - The date and time of collection - The method of collection - The urine volume and the centrifugation protocol - The number of red cells per high-power field - The number of white cells per high-power field - The number and type of casts per low-power field - The type and number of crystals - The presence of bacteria, parasites, or other formed elements The records should be maintained in the animal's medical record. The records are used to track the progression of the disease and the response to the management. ### Quality Control The quality of the urine sediment examination depends on the standardization of the procedure. The following quality controls should be in place: - The use of a standardized centrifugation protocol - The use of a fixed urine volume - The use of a fixed resuspension volume - The use of a standardized reporting format - The use of a quality control sample to verify the performance of the procedure The quality control sample is a urine sample with a known number of formed elements. The sample is examined to verify the accuracy of the procedure. The quality control is performed on a regular basis. ## Common Failure Patterns ### Delayed Examination The most common failure is the delayed examination of the urine sample. The delay leads to the degeneration of cells, the formation of crystals, and the overgrowth of bacteria. The results of the delayed examination are not reliable. The urine sample should be examined within 30 minutes of collection. If the examination is delayed, the sample should be refrigerated and examined within a few hours. The sample should not be left at room temperature. ### Inadequate Standardization The lack of standardization of the procedure is a common failure. The use of different urine volumes, centrifugation speeds, and resuspension volumes leads to inconsistent results. The results are not comparable between samples or between patients. The procedure should be standardized and followed consistently. The standardization is necessary for the reliable interpretation of the results. ### Misidentification of Formed Elements The misidentification of formed elements is a common failure. The misidentification of renal tubular cells as white cells or the misidentification of crystals as other crystals can lead to an incorrect diagnosis. The identification of formed elements requires training and experience. The use of stains can improve the identification of the formed elements. The use of a reference is recommended. ### Overinterpretation of Findings The overinterpretation of the findings is a common failure. The presence of crystals in the sediment is not always clinically significant. The presence of a few red cells is not always a sign of disease. The interpretation of the findings should be based on the clinical presentation and the other laboratory findings. The findings should be interpreted in the context of the animal's health. ## Limitations and Safety Context The urine sediment examination is a valuable diagnostic test, but it has limitations. The test is subjective and depends on the experience of the examiner. The test is not a definitive test for any disease. The urine sediment examination is a screening test. The findings are used to guide the clinical management. The definitive diagnosis is based on the clinical presentation, the other laboratory findings, and the response to the treatment. The urine sediment examination is a safe procedure. The urine sample is collected from the animal. The procedure does not cause any harm to the animal. The procedure is performed in the laboratory. The safety of the laboratory personnel is important. The urine sample is a biological material. The personnel should wear gloves and other protective equipment. The sample should be handled in a safe manner. ## Professional Escalation Criteria The following findings require the escalation of the case to a veterinarian: - The presence of renal tubular cells or casts in the sediment - The presence of a large number of red cells or white cells in the sediment - The presence of bacteria in the sediment with clinical signs of a urinary tract infection - The presence of crystals with clinical signs of urolithiasis - The presence of any formed element that is not clearly identified The veterinarian will perform a clinical examination and may recommend additional tests. The additional tests may include a urine culture, a blood test, or an imaging study. The veterinarian will determine the diagnosis and the management of the animal. The management may include the treatment of the underlying disease, the management of the urinary tract, and the prevention of the recurrence. ## Decision Framework for Sediment Interpretation and Case Management ### Structured Interpretation Logic The interpretation of urine sediment findings requires a systematic approach that moves beyond simple identification of formed elements. A structured decision framework helps the clinician integrate sediment findings with urine chemistry, physical properties, and clinical presentation to reach a defensible diagnostic conclusion. The framework presented here organizes the interpretation process into sequential decision points that reduce the risk of overinterpretation and missed findings. The first decision point is the assessment of sample quality. The collection method, the time between collection and examination, and the preparation protocol determine the reliability of the sediment findings. A sample that was collected by free catch, examined after two hours, or prepared with an inconsistent centrifugation protocol cannot support the same interpretive confidence as a fresh cystocentesis sample processed under standardized conditions. The clinician should record the sample quality parameters before proceeding to the interpretation of the formed elements. The second decision point is the correlation of sediment findings with the urine specific gravity and dipstick chemistry. The urine specific gravity determines the expected concentration of formed elements. A dilute urine sample with a specific gravity below 1.010 will have fewer cells and casts per high-power field than a concentrated sample with a specific gravity above 1.030, even when the same pathologic process is present. The dipstick findings for protein, blood, leukocyte esterase, and nitrite provide complementary information that either supports or contradicts the sediment findings. The third decision point is the integration of the sediment findings with the clinical signs. The presence of white blood cells and bacteria in the sediment of an animal with dysuria and pollakiuria supports a urinary tract infection. The same findings in an asymptomatic animal may represent contamination or a subclinical infection. The clinical context determines the urgency and the extent of the diagnostic workup. The fourth decision point is the selection of the management action. The management action may be immediate treatment, additional diagnostic testing, or monitoring with a repeat examination. The decision is based on the severity of the findings, the clinical presentation, and the risk of progression. ### Decision Point One: Sample Quality Assessment The sample quality assessment is the first step in the interpretation framework. The clinician must determine whether the sample is adequate for the diagnostic question. The adequacy of the sample is determined by the collection method, the time between collection and examination, and the preparation protocol. The collection method is recorded at the time of collection. A free catch sample is appropriate for routine screening but is prone to contamination from the distal urethra, genital tract, and perineum. The presence of squamous epithelial cells in a free catch sample is expected and does not indicate pathology. A cystocentesis sample is the preferred method for the diagnosis of a urinary tract infection because it avoids contamination from the lower urinary tract and the genital tract. The time between collection and examination is recorded. The urine sediment examination should be performed within 30 minutes of collection. If the examination is delayed, the sample should be refrigerated and examined within a few hours. The delay leads to the degeneration of cells, the formation of crystals, and the overgrowth of bacteria. The results of a delayed examination are not reliable. The preparation protocol is recorded. The urine volume, the centrifugation speed, and the centrifugation time are recorded. The resuspension volume is recorded. The standardization of the preparation protocol ensures that the results are comparable between samples and between laboratories. The sample quality assessment is recorded in the medical record. The assessment is used to determine the confidence in the sediment findings. A sample with a high quality assessment supports a high confidence in the findings. A sample with a low quality assessment supports a low confidence in the findings. ### Decision Point Two: Correlation with Urine Chemistry The urine chemistry provides complementary information that supports or contradicts the sediment findings. The urine specific gravity is the most important chemistry parameter for the interpretation of the sediment. The specific gravity determines the concentration of the urine and the expected number of formed elements per high power field. A urine sample with a specific gravity below 1.010 is dilute. The dilute urine will have fewer cells and casts per high power field than a concentrated sample. The absence of cells and casts in a dilute sample does not exclude the presence of a pathologic process. The clinician should consider the specific gravity when interpreting the sediment findings. A urine sample with a specific gravity above 1.030 is concentrated. The concentrated urine will have more cells and casts per high power field. The presence of a few cells in a concentrated sample may be normal. The presence of a large number of cells in a concentrated sample is more likely to be clinically significant. The dipstick chemistry provides information about the presence of protein, blood, leukocyte esterase, and nitrite. The protein is a measure of the protein in the urine. The protein can be present in the urine with renal disease, urinary tract inflammation, or contamination. The blood is a measure of the red cells in the urine. The blood can be present with hemorrhage, inflammation, or contamination. The leukocyte esterase is a measure of the white cells in the urine. The leukocyte esterase is present with inflammation. The nitrite is a measure of the bacteria in the urine. The nitrite is present with a bacterial infection. The urine chemistry is interpreted with the sediment findings. The presence of protein in the urine with casts in the sediment supports a renal disease. The presence of blood in the urine with red cells in the sediment supports a hemorrhage. The presence of leukocyte esterase in the urine with white cells in the sediment supports an inflammation. The presence of nitrite in the urine with bacteria in the sediment supports a bacterial infection. ### Decision Point Three: Clinical Correlation The clinical correlation is the integration of the sediment findings with the clinical signs. The clinical signs are the symptoms that the animal is showing. The clinical signs are used to determine the significance of the sediment findings. The clinical signs of a urinary tract infection include dysuria, pollakiuria, and hematuria. The presence of white cells and bacteria in the sediment with these clinical signs supports a urinary tract infection. The presence of white cells and bacteria in the sediment without these clinical signs may be a subclinical infection or contamination. The clinical signs of a renal disease include polyuria, polydipsia, and azotemia. The presence of renal tubular cells and casts in the sediment with these clinical signs supports a renal disease. The presence of renal tubular cells and casts in the sediment without these clinical signs may be an early renal disease or a transient injury. The clinical signs of a urolithiasis include dysuria, pollakiuria, and hematuria. The presence of crystals in the sediment with these clinical signs supports a urolithiasis. The presence of crystals in the sediment without these clinical signs may be a crystalluria without a urolithiasis. The clinical context is used to determine the urgency of the management. The presence of a large number of white cells and bacteria with a fever and a depression is an emergency. The presence of a few crystals without clinical signs is a routine finding. ### Decision Point Four: Management Action Selection The management action is the final step in the decision framework. The management action is based on the severity of the findings, the clinical presentation, and the likelihood of progression. The management action may be a treatment, a follow-up test, or a routine monitoring. The treatment is the management of the underlying disease. The treatment of a bacterial urinary tract infection is the administration of an antibiotic. The treatment of a urolithiasis is the management of the crystals and the prevention of the recurrence. The treatment of a renal tubular damage is the management of the underlying cause and the support of the renal function. The follow-up test is a test that is performed to confirm the diagnosis or to monitor the response to the treatment. The follow-up test may be a urine culture, a blood test, or an imaging study. The urine culture is the definitive test for a urinary tract infection. The blood test is the test for the renal function. The imaging study is the test for the urolithiasis. The routine monitoring is a repeat examination that is performed at a regular interval. The routine monitoring is used to track the progression of the disease and the response to the treatment. The routine monitoring is performed at a regular interval, such as every two weeks or every month. The management action is recorded in the clinical record. The management action is used to track the outcome of the case. The outcome is the response to the management. ### Troubleshooting the Decision Framework The decision framework is a structured approach to the interpretation of the urine sediment. The framework is not a substitute for the clinical judgment of the veterinarian. The framework is a tool that is used to organize the interpretation and to reduce the risk of misinterpretation. The framework can fail when the sample quality is poor. The poor sample quality leads to the misinterpretation of the findings. The framework can fail when the urine chemistry is not considered. The urine chemistry provides the complementary information that is necessary for the interpretation. The framework can fail when the clinical context is not considered. The clinical context is the most important factor in the interpretation. The troubleshooting of the framework is the identification of the failure and the correction of the failure. The failure is identified by the review of the findings and the clinical presentation. The failure is corrected by the repetition of the examination with a better sample or the consideration of the additional information. ### Record System for the Decision Framework The record system for the decision framework is a standardized format for the recording of the sediment findings and the interpretation. The record system includes the sample quality assessment, the urine chemistry, the sediment findings, the clinical context, and the management action. The sample quality assessment is recorded as the collection method, the time between collection and the examination, and the preparation protocol. The urine chemistry is recorded as the specific gravity, the protein, the blood, the leukocyte esterase, and the nitrite. The sediment findings are recorded as the number of red cells, the number of white cells, the number and type of casts, the type and number of crystals, and the presence of bacteria. The clinical context is recorded as the clinical signs and the physical examination findings. The management action is recorded as the treatment, the follow-up test, or the routine monitoring. The record system is maintained in the animal's medical record. The record is used to track the progression of the disease and the response to the management. The record is used to compare the findings between the examinations. ### Comparison of the Decision Framework with the Standard Approach The standard approach to the interpretation of the urine sediment is the identification of the formed elements and the interpretation of the findings in the context of the clinical presentation. The decision framework is a structured approach that adds the sample quality assessment, the urine chemistry, and the management action selection to the standard approach. The decision framework is more time-consuming than the standard approach. The decision framework requires the recording of the sample quality, the urine chemistry, and the management action. The standard approach requires the identification of the formed elements and the interpretation of the findings. The decision framework is more reliable than the standard approach. The decision framework reduces the risk of the misinterpretation of the findings. The decision framework ensures that the sample quality, the urine chemistry, and the clinical context are considered in the interpretation. The decision framework is more useful for the monitoring of the disease. The decision framework provides a structured format for the recording of the findings and the interpretation. The structured format allows the comparison of the findings between the examinations. ### Application of the Framework to Common Clinical Scenarios The framework is applied to the common clinical scenarios to demonstrate the use of the framework. The first scenario is a dog with a urinary tract infection. The dog is presented with dysuria, pollakiuria, and hematuria. The urine is collected by cystocentesis. The sample is examined within 30 minutes. The specific gravity is 1.020. The dipstick is positive for the blood, the leukocyte esterase, and the nitrite. The sediment has a large number of white cells and bacteria. The clinical context is a urinary tract infection. The management action is the administration of an antibiotic and a urine culture. The second scenario is a cat with a chronic kidney disease. The cat is presented with polyuria, polydipsia, and a weight loss. The urine is collected by a free catch. The sample is examined within 30 minutes. The specific gravity is 1.010. The dipstick is positive for the protein. The sediment has a few granular casts and a few renal tubular cells. The clinical context is a chronic kidney disease. The management action is the management of the renal disease and the monitoring of the renal function. The third scenario is a dog with a calcium oxalate urolithiasis. The dog is presented with a dysuria and a hematuria. The urine is collected by a free catch. The sample is examined within 30 minutes. The specific gravity is 1.030. The dipstick is positive for the blood. The sediment has a large number of calcium oxalate crystals and a few red cells. The clinical context is a urolithiasis. The management action is the imaging of the urinary tract and the management of the urolithiasis. The framework is applied to the clinical scenarios to demonstrate the use of the framework. The framework is a structured approach to the interpretation of the urine sediment. The framework is used to organize the interpretation and to make the management decision. ### The Role of the Framework in the Prevention of the Misinterpretation The framework is used to prevent the misinterpretation of the urine sediment. The misinterpretation of the urine sediment is a common failure in the clinical practice. The misinterpretation is the identification of the formed elements as the wrong type or the interpretation of the findings as the wrong clinical significance. The framework prevents the misinterpretation by the standardization of the interpretation. The framework requires the assessment of the sample quality, the correlation of the urine chemistry, and the integration of the clinical context. The framework reduces the risk of the misinterpretation by the consideration of the additional information. The framework prevents the misinterpretation of the renal tubular cells as the white cells. The renal tubular cells are larger than the white cells and have a round nucleus. The framework requires the identification of the cell type and the correlation with the urine chemistry. The presence of the renal tubular cells with the casts and the proteinuria supports the renal tubular damage. The framework prevents the misinterpretation of the crystals as the other crystals. The crystals are identified by the shape, the color, and the refractive index. The framework requires the identification of the crystal type and the correlation with the urine pH. The presence of the struvite crystals with a high urine pH supports the struvite urolithiasis. The framework prevents the misinterpretation of the bacteria as the contamination. The bacteria are present in the sediment with the white cells and the clinical signs. The framework requires the correlation of the bacteria with the clinical context. The presence of the bacteria with the white cells and the clinical signs supports the urinary tract infection. ### The Framework and the Professional Escalation The framework is used to determine the professional escalation. The professional escalation is the referral of the case to a veterinarian. The framework identifies the findings that require the escalation. The presence of the renal tubular cells and the casts in the sediment requires the escalation. The presence of the renal tubular cells and the casts indicates the renal tubular injury. The injury may be caused by the nephrotoxin, the ischemia, or the infection. The veterinarian will perform the clinical examination and may recommend the additional tests. The presence of a large number of the red cells and the white cells in the sediment requires the escalation. The presence of a large number of the red cells and the white cells indicates the hemorrhage and the inflammation. The veterinarian will perform the clinical examination and may recommend the additional tests. The presence of the bacteria in the sediment with the clinical signs of the urinary tract infection requires the escalation. The presence of the bacteria with the clinical signs supports the urinary tract infection. The veterinarian will perform the clinical examination and may recommend the urine culture. The presence of the crystals with the clinical signs of the urolithiasis requires the escalation. The presence of the crystals with the clinical signs supports the urolithiasis. The veterinarian will perform the clinical examination and may recommend the imaging study. The framework is used to the professional escalation. The framework is a structured approach to the interpretation of the urine sediment. The framework is used to the management of the case. ## Frequently Asked Questions ### What is the difference between a renal tubular cell and a transitional epithelial cell? Renal tubular cells are smaller than transitional epithelial cells and have a round nucleus. They are present in the sediment when there is renal tubular injury. Transitional epithelial cells are larger and have a moderate amount of cytoplasm. They are present in the sediment when there is inflammation or neoplasia of the bladder or ureter. ### How long can urine be stored before sediment examination? Urine should be examined within 30 minutes of collection. If the examination is delayed, the sample should be refrigerated and examined within a few hours. Refrigeration slows the degeneration of the cells and the formation of crystals, but it does not stop the changes. ### What is the clinical significance of a few crystals in the urine? The presence of a few crystals in the urine is not always clinically significant. Crystals can be present in normal urine. The clinical significance is determined by the type of crystal, the number of crystals, and the clinical presentation. The presence of crystals with clinical signs of urolithiasis is significant. ### What is the difference between a granular cast and a cellular cast? A granular cast is composed of protein and cellular debris. It indicates renal tubular injury. A cellular cast is composed of red cells, white cells, or epithelial cells. It indicates a specific type of renal injury. The presence of a cellular cast is more specific than the presence of a granular cast. ### How is the urine sediment examination used to diagnose a urinary tract infection? The urine sediment examination is used to identify the presence of white cells and bacteria in the urine. The presence of white cells and bacteria with clinical signs of a urinary tract infection supports the diagnosis. The definitive diagnosis is based on the urine culture. ### What is the difference between a free catch and a cystocentesis sample? A free catch sample is collected by catching the urine as the animal urinates. It is less invasive but is prone to contamination. A cystocentesis sample is collected by inserting a needle into the bladder. It is more invasive but is a sterile sample. The cystocentesis sample is preferred for the diagnosis of a urinary tract infection. ### What is the clinical significance of a renal tubular cell in the urine? The presence of a renal tubular cell in the urine indicates renal tubular injury. The injury can be caused by a nephrotoxin, ischemia, or infection. The finding is a specific indicator of renal tubular damage. ### What is the clinical significance of a hyaline cast in the urine? A hyaline cast is composed of protein. It is present in concentrated urine, after exercise, or with proteinuria. It is not always clinically significant. The presence of a hyaline cast with other findings, such as granular casts, suggests renal disease. ## Using the Evidence | Source | Best use in this topic | Important limitation | |---|---|---| | [Pet Care](https://www.avma.org/resources-tools/pet-owners) | official guidance | Check the linked page for current local requirements | | [AAHA Guidelines](https://www.aaha.org/resources) | official guidance | Check the linked page for current local requirements | | [Global Guidelines](https://wsava.org/global-guidelines) | official guidance | Check the linked page for current local requirements | ## Related Veterinary Guides - [Anesthesia for Patients with Urinary Obstruction: Metabolic Concerns](/knowledge/veterinary-medicine/anesthesia-analgesia/anesthesia-patients-urinary-obstruction-metabolic-concerns) - [Anesthesia for Patients with Urinary Incontinence: Urethral Sphincter Surgery](/knowledge/veterinary-medicine/anesthesia-analgesia/anesthesia-patients-urinary-incontinence-urethral-sphincter-surgery) - [Azotemia in Veterinary Patients: Prerenal, Renal, and Postrenal Differentiation and Fluid Reassessment](/knowledge/veterinary-medicine/clinical-methods/azotemia-veterinary-prerenal-renal-postrenal-differentiation-fluid-reassessment) - [Proteinuria in Veterinary Patients: Confirmation, Quantification, Blood Pressure, and Renal Workup](/knowledge/veterinary-medicine/clinical-methods/proteinuria-veterinary-confirmation-quantification-blood-pressure-renal-workup) - [Anesthesia for Patients with Renal or Hepatic Disease: Drug Selection and Dosing Adjustments](/knowledge/veterinary-medicine/anesthesia-analgesia/anesthesia-renal-hepatic-disease-drug-selection-dosing) ## References and Further Reading - [Pet Care](https://www.avma.org/resources-tools/pet-owners). American Veterinary Medical Association. - [AAHA Guidelines](https://www.aaha.org/resources). American Animal Hospital Association. - [Global Guidelines](https://wsava.org/global-guidelines). World Small Animal Veterinary Association. - [Merck Veterinary Manual](https://www.merckvetmanual.com/). Merck Veterinary Manual. - [Cornell University College of Veterinary Medicine](https://www.vet.cornell.edu/). Cornell University. - [Animal Health and Welfare](https://www.woah.org/en/what-we-do/animal-health-and-welfare). World Organisation for Animal Health. - [Importance of Urinalysis.](https://pubmed.ncbi.nlm.nih.gov/30591190). The Veterinary clinics of North America. Small animal practice, 2019. - [Urinalysis.](https://pubmed.ncbi.nlm.nih.gov/26002794). The Veterinary clinics of North America. Small animal practice, 2015. - [Urine sediment examination: Potential impact of red and white blood cell counts using different sediment methods.](https://pubmed.ncbi.nlm.nih.gov/30537173). Veterinary clinical pathology, 2018. - [[Urinalysis in dogs and cats, part 2: Urine sediment analysis].](https://pubmed.ncbi.nlm.nih.gov/37956665). Tierarztliche Praxis. Ausgabe K, Kleintiere/Heimtiere, 2023. - [Bacterial urinary tract infections.](https://pubmed.ncbi.nlm.nih.gov/8711864). The Veterinary clinics of North America. Small animal practice, 1996. > This article is educational and is not a substitute for veterinary diagnosis or treatment. Contact a veterinarian for advice about an individual animal.