Radiographic Assessment of Peritoneal Dialysis Catheter Placement in Cats

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-11

Key Takeaways

• Radiography is the primary modality for assessing peritoneal dialysis (PD) catheter placement and function in cats, confirming intraperitoneal tip location, ensuring the fenestrated segment is within the peritoneal cavity, and evaluating for migration or kinking.
• Optimal catheter tip placement is in the caudal abdomen within the peritoneal cavity, ideally following a smooth arc without kinks or acute angulation to prevent impaired dialysate flow and potential catheter fracture.
• Common radiographic complications include omental wrapping (visualized as a soft tissue opacity mass around the tip), fluid loculation (asymmetric soft tissue opacities indicating compartmentalized fluid), and pericatheter gas or swelling (suggesting leakage or infection).
• Orthogonal radiographic projections (lateral and ventrodorsal) are essential for a comprehensive assessment, with the lateral view best for craniocaudal tip position and the ventrodorsal view for detecting lateral deviation.
• Contrast radiography, involving injection of water-soluble iodinated contrast medium, is indicated when plain radiographs are inconclusive to assess catheter lumen patency, contrast distribution for omental wrapping or adhesions, and for detecting extraperitoneal leakage.
• Serial radiographic monitoring, comparing current images to an immediate post-placement baseline, is crucial for detecting subtle catheter migration or changes in position that may precede overt clinical malfunction.

Peritoneal dialysis is a renal replacement modality used in feline patients with acute kidney injury or end-stage renal disease when hemodialysis is unavailable or impractical. The functional lifespan of the dialysis catheter depends on correct placement, secure fixation, and the absence of complications that impair fluid exchange. Radiography provides the primary imaging method for verifying catheter position after placement and for investigating malfunction during the treatment course. This article addresses the radiographic evaluation of peritoneal dialysis catheters in cats, covering normal radiographic anatomy, criteria for acceptable positioning, and the imaging features of common complications. The content is directed at practicing veterinarians who perform or interpret radiographs in feline patients undergoing peritoneal dialysis.

The clinical questions that radiography answers include whether the catheter tip lies within the peritoneal cavity, whether the fenestrated segment is positioned to permit adequate dialysate flow, whether the catheter has migrated or become entrapped, and whether complications such as omental wrapping, fluid loculation, or infection-related changes are present. Radiographic assessment complements physical examination findings such as poor inflow or outflow, pericatheter leakage, or pain on infusion. Serial radiographs provide a baseline for comparison when dysfunction develops days or weeks after placement.

At a Glance

Principles of Catheter Design Relevant to Radiographic Interpretation

Peritoneal dialysis catheters for cats are typically silicone or polyurethane tubes with a radiopaque stripe or marker that permits radiographic visualization. Most catheters used in feline patients are modified versions of human pediatric catheters or veterinary-specific designs. The catheter has three functional zones: an intraperitoneal segment containing fenestrations or side holes, a subcutaneous tunnel segment, and an external segment connecting to the dialysis tubing. One or two Dacron cuffs anchor the catheter within the body wall and subcutaneous tissues, creating a barrier against bacterial migration.

The fenestrated portion must lie entirely within the peritoneal cavity for effective dialysis. If the fenestrations sit within the body wall or subcutaneous space, dialysate will track along the catheter tract instead of entering the peritoneal cavity. Radiographic assessment therefore requires identification of the fenestrated zone, which may be visible as a region of altered opacity or as a distinct segment demarcated by radiopaque markers on some catheter designs. When the catheter lacks visible fenestration markers, the radiologist must infer the fenestrated zone from the known catheter dimensions and the position of the cuffs, which are occasionally radiopaque.

The peritoneal cavity in cats extends from the diaphragm to the pelvic inlet. The catheter tip should ideally lie in the caudal abdomen, within the dependent portion of the peritoneal cavity, where dialysate pools during drainage. The caudal abdominal location minimizes the distance dialysate must travel and reduces the risk of the omentum enveloping the tip. Cranial placement within the omental bursa or between liver lobes increases the risk of poor drainage and omental wrapping.

Normal Radiographic Appearance

On a lateral radiograph of a cat in right or left recumbency, the correctly placed catheter appears as a smooth, continuous radiopaque line entering the ventral abdominal wall, passing through the body wall, and coursing caudally within the peritoneal cavity. The intraperitoneal portion typically follows a gentle curve along the ventral abdominal floor, with the tip positioned in the caudal third of the abdomen, dorsal to the bladder when the bladder is distended. The catheter should not cross the spine, should not enter the retroperitoneal space, and should not pass through solid organs.

The ventrodorsal projection confirms that the catheter remains within the midline or paramedian position and has not deviated laterally into the body wall. The catheter should not overlie the kidneys, spleen, or intestinal mass in a way that suggests parenchymal penetration. Gas within the peritoneal cavity may be present immediately after placement, a normal finding that resolves within days. The presence of a small volume of dialysate in the peritoneal cavity produces a generalized increase in abdominal soft tissue opacity with loss of serosal detail, which is expected during active dialysis.

The subcutaneous tunnel segment appears as a straight or gently curved radiopaque line within the ventral body wall. The angle at which the catheter enters the peritoneal cavity should be oblique instead of perpendicular, reducing the risk of kinking at the entry point. The cuffs, when visible, should lie within the subcutaneous tissues and the rectus sheath respectively, not within the peritoneal cavity itself.

Radiographic Projections and Technique

Two orthogonal projections, a lateral and a ventrodorsal view, constitute the minimum radiographic study for evaluating peritoneal dialysis catheter position. The lateral projection provides the most information about catheter course, tip location, and the relationship of the fenestrated segment to the body wall. The ventrodorsal projection is essential for detecting lateral deviation of the catheter into the body wall or flank, which the lateral view may miss. Additional oblique projections can help separate the catheter from overlying structures when the tip is obscured by intestinal contents or fecal material.

Radiographs should be obtained with the cat in a consistent position to allow meaningful comparison between studies. The same recumbency should be used for serial evaluations. Full inspiration or expiration does not materially alter catheter position, but the degree of bladder distension affects the apparent location of the catheter tip relative to other abdominal structures. A distended bladder displaces the intestinal mass cranially and may alter the catheter course. When possible, obtain radiographs before voiding or after a consistent period of fasting to standardize abdominal conformation.

The exposure technique should be adjusted for the cat's body condition. Obese cats require higher kilovoltage settings to penetrate the increased soft tissue mass, and the catheter may be more difficult to visualize against a background of intra-abdominal fat. Digital radiography systems allow windowing and leveling adjustments that can enhance catheter visibility. Magnification views of the catheter entry site can help identify subtle kinks or cuff malposition. The American College of Veterinary Radiology resources provide guidance on imaging standards and radiation safety practices that apply to serial radiographic monitoring in feline patients.

Radiographic Assessment of Catheter Function

Radiographic findings must be correlated with the clinical performance of the catheter. A catheter that appears radiographically well positioned may still malfunction if omental wrapping or fibrinous adhesions develop around the fenestrations without producing a visible mass. Conversely, a catheter with mild tip migration may continue to function adequately. The radiograph provides anatomic information, while the dialysis cycle provides functional information. Both are required for complete assessment.

The MSD Veterinary Manual describes peritoneal dialysis as a procedure requiring careful catheter management and monitoring for complications, including catheter obstruction, leakage, and infection. Radiographic evaluation forms part of this monitoring protocol, particularly when inflow or outflow volumes decline. The decision to revise or replace a catheter should integrate radiographic findings with the duration of dysfunction, the presence of fever or peritoneal pain, and the results of dialysate analysis.

Radiographic Checklist for Catheter Position

A structured checklist reduces the risk of overlooking a subtle malposition. Evaluate every study against the following criteria, regardless of the indication for imaging.

Catheter tip position

• Tip located within the peritoneal cavity, caudal to the liver and spleen
• Tip not embedded within omental fat, mesenteric reflections, or solid organs
• Tip not folded back on itself or coiled within a loculated fluid pocket
• Tip position stable when compared with the immediate post-placement study, if available

Catheter course

• Catheter follows a smooth, uninterrupted path from the body wall to the tip
• No acute angulation, kinking, or buckling along the intraperitoneal segment
• No evidence of the catheter passing through omental fat in a tortuous or redundant loop
• Subcutaneous tunnel segment, when visible, shows no looping or tenting at the skin entry site

Catheter integrity

• No radiopaque marker discontinuity, if the catheter has a radiopaque stripe or bead
• No fragmentation, cracking, or separation of catheter segments
• Side holes and the distal fenestrated segment, when opacified by contrast, appear patent

Soft tissue and fluid signs

• Peritoneal fluid volume subjectively assessed for increase or decrease from prior studies
• No gas lucencies within the peritoneal cavity that would suggest recent air introduction or visceral perforation
• No soft tissue opacity mass effect adjacent to the catheter tip that would suggest omental wrapping or abscess formation

Bone and body wall

• No rib fracture, vertebral lesion, or pelvic fracture that would alter catheter trajectory
• Body wall thickness at the catheter exit site assessed for subcutaneous emphysema or fluid tracking

Record each criterion as normal, abnormal, or indeterminate. An indeterminate finding on a single projection warrants an orthogonal view or a contrast study before clinical decisions are made.

Decision Tree for Suspected Catheter Malfunction

Malfunction presents clinically as slow inflow, poor outflow, or both. The radiographic evaluation follows a logical sequence that begins with the least invasive assessment and progresses to contrast studies only when plain radiography is unrewarding.

Step 1: Confirm catheter identity and position on plain radiographs

Obtain right lateral and ventrodorsal projections. Compare with the most recent prior study. If the tip has migrated, changed orientation, or the catheter has become kinked, this alone may explain the malfunction. A catheter that has withdrawn into the subcutaneous tissues or omental fat will frequently produce poor drainage without complete obstruction.

Step 2: Assess peritoneal fluid volume and distribution

A marked increase in peritoneal fluid with a normally positioned catheter suggests outflow failure instead of inflow failure. A loculated fluid pocket, visible as a soft tissue opacity with a convex border adjacent to the catheter tip, may indicate that the fenestrated segment has become walled off by omentum or adhesions.

Step 3: Perform a contrast study when plain radiographs are inconclusive

Inject 5 to 10 mL of water-soluble iodinated contrast medium through the catheter under aseptic technique. Obtain immediate and delayed radiographs. The contrast study answers three questions:

Contrast that pools immediately around the tip and does not disperse over 5 to 10 minutes supports omental entrapment. Contrast that tracks retrograde along the catheter tunnel indicates a tunnel leak, which may require catheter replacement. Contrast that fails to leave the catheter lumen entirely suggests intraluminal obstruction from a clot or fibrin plug.

Step 4: Integrate radiographic findings with clinical parameters

Radiographic findings must be interpreted alongside drainage volumes, inflow times, and effluent character. A catheter that appears radiographically normal but drains poorly may have a functional problem such as omental wrapping that is not visible on plain radiographs. In this setting, ultrasonography can complement radiography by directly visualizing the catheter tip and surrounding omentum. The American College of Veterinary Radiology resources provide guidance on selecting the appropriate imaging modality and on radiation safety practices for serial studies.

Step 5: Decide between catheter manipulation and replacement

A catheter that is kinked or folded may be repositioned with gentle manipulation under fluoroscopic guidance, if available. A catheter that has migrated into the subcutaneous tissues, has a tunnel leak, or is walled off by omentum will rarely function reliably after manipulation and should be replaced. Repeated manipulation of a malpositioned catheter increases the risk of peritoneal contamination and should be avoided.

Monitoring Parameters for Serial Radiographic Assessment

Serial radiographs serve two purposes: confirming continued correct position and detecting complications before they become clinically apparent. The frequency of monitoring depends on patient status and catheter function.

Radiographs obtained at 24 to 48 hours after placement establish a baseline for comparison. Subsequent imaging is indicated when malfunction develops, when the catheter is manipulated, or when clinical signs suggest a complication. Routine weekly radiographs in a stable patient add little information and expose the patient to unnecessary radiation. The MSD Veterinary Manual provides general guidance on the indications for serial imaging in feline patients with indwelling devices.

Documentation of Radiographic Findings

Document each study systematically in the medical record. Include the projection, the catheter tip location relative to bony landmarks or viscera, the catheter course, the presence or absence of kinking, and the peritoneal fluid volume. Record the catheter type and lot number if a radiopaque marker is present, as this aids in identifying the fenestrated segment on subsequent studies.

For contrast studies, document the contrast agent, volume, concentration, and the time interval between injection and imaging. Describe the distribution pattern using standard terminology: free dispersion, loculated pooling, retrograde tracking, or extraperitoneal leakage. Include a recommendation for follow-up imaging or intervention when findings are abnormal.

Serial comparison is only possible when prior studies are available for review. Store images in a format that allows side-by-side comparison with the current study, and note any interval change explicitly in the record. A catheter that has not moved, has not kinked, and shows no fluid accumulation may still malfunction, and the record should state that radiographic findings do not exclude functional obstruction.

Limitations of Radiographic Assessment

Radiography cannot visualize the catheter tip directly unless the catheter is radiopaque or contrast is administered. Many feline peritoneal dialysis catheters have a radiopaque stripe or bead at the tip, but the fenestrated segment may not be visible without contrast. Plain radiographs also cannot distinguish between omental wrapping and simple adhesion formation, both of which produce similar soft tissue opacity changes.

Ultrasonography offers complementary information by directly visualizing the catheter tip, the surrounding omentum, and the peritoneal fluid in real time. When available, ultrasound should be used to confirm or exclude omental entrapment before a catheter is removed. The choice between radiography and ultrasonography depends on equipment availability and operator experience, and both modalities may be required in a single case.

Patient status changes the correct approach. A critically ill cat with suspected visceral perforation requires immediate surgical assessment instead of extensive imaging. A stable cat with gradual loss of drainage efficiency can undergo a contrast study without the same urgency. Production setting and available equipment also influence the sequence: fluoroscopy-guided manipulation is feasible in referral practice but not in general practice, where catheter replacement may be the only option for a kinked catheter.

Recognized Complications and Early Radiographic Detection

Peritoneal dialysis catheter malfunction in cats usually falls into one of several recognizable patterns, each with a characteriztic radiographic signature. Early detection depends on comparing the current study with the immediate post-placement radiograph, because minor positional changes that are clinically silent may precede overt failure.

Omental wrapping or entrapment. The omentum can envelop the intraperitoneal portion of the catheter, obstructing the side holes. Radiographs may show the catheter tip displaced from its original position, often curled or folded back on itself, with a soft tissue opacity surrounding the tip. The discriminating feature is that the catheter lumen remains visible and continuous, but the tip no longer lies freely within the peritoneal cavity. Serial radiographs showing progressive tip migration toward the omentum or a change in the catheter's curvature support this diagnosis.

Catheter migration. The catheter tip may drift from the caudal abdomen into the cranial abdomen, or become lodged between viscera. This is detected by comparing the tip position relative to fixed bony landmarks such as the pelvic inlet or the last rib. A tip that has moved more than one vertebral body length from its placement position warrants attention, particularly if drainage has become sluggish.

Kinking or folding. Acute angulation of the catheter, usually at the point where it passes through the body wall or at the junction between the subcutaneous and intraperitoneal segments, produces a visible reduction in lumen diameter. Radiographs in two orthogonal projections are essential, because a kink may be invisible in a single view if the fold is oriented perpendicular to the beam.

Catheter fracture or leakage. Discontinuity of the radiopaque line, or contrast extravasation along the catheter tract, indicates structural failure. If leakage is suspected but not visible on plain radiographs, injection of water-soluble iodinated contrast through the catheter under fluoroscopic or radiographic guidance can confirm the site of extravasation.

Malposition within the peritoneal cavity. The catheter tip should lie within the dependent portion of the peritoneal cavity, typically the caudal abdomen. A tip positioned cranially, dorsally, or within the omental bursa reduces drainage efficiency. The lateral projection is most useful for assessing craniocaudal position, while the ventrodorsal projection confirms whether the tip has deviated laterally.

Common Errors in Radiographic Interpretation

Less experienced clinicians frequently misinterpret normal findings as complications, or overlook subtle abnormalities that precede failure. The most common error is assessing catheter position on a single projection. A catheter that appears malpositioned on one view may be perfectly placed when the orthogonal view is examined. Conversely, a kink that is invisible on the lateral view may be obvious on the ventrodorsal projection.

A second error is failing to obtain a baseline post-placement radiograph. Without this reference, distinguishing normal migration from pathological displacement is impossible. The immediate post-placement study should be treated as the standard against which all subsequent studies are compared.

A third error is overinterpreting the significance of the catheter tip touching viscera. The tip commonly contacts bowel or omentum without causing obstruction. The relevant question is whether the side holes remain patent and whether drainage is adequate, not whether the tip lies in a geometrically perfect position.

Finally, clinicians sometimes attribute poor drainage to catheter malposition when the cause is actually fibrin clot within the lumen, which is not visible radiographically. If the catheter position appears unchanged and satisfactory, the radiographic study has excluded a positional cause, and the clinician should pursue other explanations for malfunction.

Limitations of Current Evidence and Areas of Expert Disagreement

Published evidence specifically addressing radiographic assessment of peritoneal dialysis catheters in cats is limited. Most guidance is extrapolated from human nephrology literature or from general veterinary interventional radiology principles. The American College of Veterinary Radiology resources provide standards for imaging technique and radiation safety, but do not offer species-specific criteria for catheter position assessment.

Expert opinion differs on several points. There is no consensus on the optimal radiographic projection for assessing tip position, although most practitioners favour the lateral view for craniocaudal assessment. There is also disagreement about how much tip migration is acceptable before intervention is warranted. Some clinicians accept up to two vertebral body lengths of migration if drainage remains adequate, while others recommend repositioning at the first sign of movement.

The role of contrast radiography in evaluating catheter function is similarly debated. Some authors advocate routine contrast studies when malfunction is suspected, while others reserve contrast for cases where plain radiographs are inconclusive. The evidence base does not resolve this disagreement, and clinical judgment should guide the decision.

Referral, Specialist Consultation, and Reporting

Referral to a veterinary radiologist or interventionalist is warranted when plain radiographs cannot explain persistent catheter malfunction, when contrast studies are required, or when the clinician is uncertain whether repositioning is feasible. Specialist consultation is also appropriate when serial radiographs show progressive migration that may require surgical correction.

Laboratory involvement is indicated when radiographic findings suggest peritonitis, such as unexplained soft tissue opacity or free gas within the peritoneal cavity. Cytology and culture of drained fluid should accompany radiographic assessment in these cases.

Regulatory reporting obligations vary by jurisdiction. In most regions, complications arising from veterinary procedures do not require mandatory reporting, but clinicians should be aware of local requirements. The American Veterinary Medical Association practice resources and WOAH terrestrial animal health standards provide general guidance on professional obligations, though neither addresses dialysis catheter complications specifically. When in doubt about reporting requirements, consultation with the relevant professional body or regulatory authority is appropriate.

Frequently Asked Questions

How should I proceed if only a single lateral projection is feasible in a fractious or unstable cat?

A single lateral view remains diagnostically useful, but it cannot confirm three-dimensional position. The key limitation is craniocaudal assessment: the catheter tip may appear correctly positioned within the peritoneal cavity while actually lying within the omental bursa or against the body wall. If a ventrodorsal view is unsafe, consider a horizontal-beam dorsoventral projection with the cat in sternal recumbency, which often requires less restraint. Alternatively, a right or left lateral decubitus view with a horizontal beam can help identify free peritoneal fluid. When only one view is possible, document the limitation explicitly and recommend a follow-up orthogonal study once the patient is stable. The American College of Veterinary Radiology resources provide guidance on adapting projections to patient compromise.

What radiographic findings distinguish intraperitoneal from subcutaneous catheter placement?

Subcutaneous placement typically shows the catheter coursing parallel to the body wall with its tip outside the peritoneal silhouette, often with a visible soft tissue stripe separating the catheter from the abdominal organs. Intraperitoneal placement shows the catheter tip within the peritoneal cavity, with loops of small intestine or falciform fat adjacent to it. A lateral projection alone can be misleading because a subcutaneous catheter overlying the abdomen may appear intraperitoneal. The ventrodorsal view is more reliable: a subcutaneous catheter follows the flank contour, whereas an intraperitoneal catheter crosses the peritoneal cavity and may shift position between projections. If contrast is needed, inject 1 to 2 mL of iodinated contrast medium through the catheter and repeat radiography, but consult current formulary guidance for appropriate agents and volumes.

How does radiographic assessment differ in a kitten compared with an adult cat?

Kittens have a smaller peritoneal cavity, thinner body walls, and less falciform fat, which reduces natural contrast around the catheter tip. The tip may lie closer to the bladder or spleen, and the catheter may curl more easily because of the short distance from the insertion site to the dependent portion of the abdomen. A lateral projection in a kitten often shows the catheter following a tighter curve, and the tip may sit more cranially than expected. The ventrodorsal view is especially important in kittens because the catheter can migrate into the omental bursa more readily. Growth over the course of dialysis may alter catheter position, so serial radiographs should be compared with the immediate post-placement study instead of with published normal values.

What should I record in the medical record after each radiographic assessment?

Record the date, the projections obtained, the catheter type and insertion site, and the measured distance from the insertion site to the tip. Describe the catheter course, including any loops, kinks, or abrupt angulation, and state the tip location relative to named anatomic landmarks such as the caudal pole of the kidney or the pelvic inlet. Note whether the tip moved compared with the previous study. Document the presence or absence of free peritoneal fluid, peritoneal thickening, or gas locules. Record the functional assessment, including whether contrast medium flowed freely and whether any was seen outside the peritoneal cavity. The AVMA practice resources offer general guidance on medical record standards that apply to imaging documentation.

How do I explain radiographic findings to an owner whose cat has a malpositioned catheter?

Use plain language and a simple diagram. Explain that the catheter has moved from its intended position and that this can reduce dialysis efficiency or cause discomfort. State whether the catheter can be repositioned without surgery or whether replacement is needed. Describe the risks of leaving it in place, including poor drainage, omental wrapping, or organ irritation. Give the owner a realistic timeline: repositioning may require a short anesthetic, and replacement may require a second procedure. If the catheter is functional despite a suboptimal position, explain why serial monitoring is recommended and what changes would prompt intervention. Avoid overstating certainty, because some malpositions are tolerated for long periods. The MSD Veterinary Manual provides background on peritoneal dialysis complications that can support owner discussions.

When is ultrasonography preferable to radiography for evaluating a dialysis catheter?

Ultrasonography is superior when the catheter tip is not clearly visible radiographically, when soft tissue detail is obscured by peritoneal fluid, or when omental wrapping is suspected. It can identify the tip as a hyperechoic line with distal shadowing and can show surrounding fluid pockets or adhesions. Ultrasonography also allows real-time assessment of catheter movement during infusion and drainage. However, it is operator dependent and may not visualize the entire catheter course, particularly in the cranial abdomen. Radiography remains the first-line modality for confirming overall position and detecting kinks or loops. Use ultrasonography as an adjunct when radiography is inconclusive or when a specific complication such as omental entrapment is suspected. The ACVR resources describe the complementary roles of imaging modalities in small animal practice.

Related Clinical & Scientific Guides

• MRI Monitoring of Brain Tumor Response to Therapy in Dogs
• Ultrasound-Guided Drainage of Abscesses in Small Animals
• Radiographic Monitoring of Total Hip Replacement in Dogs

References and Further Reading

• Biofield therapies: helpful or full of hype? A best evidence synthesis.. 2010.
• Infectious Disease Transmission in Solid Organ Transplantation: Donor Evaluation, Recipient Risk, and Outcomes of Transmission.. 2019.
• American College of Veterinary Radiology Resources. American College of Veterinary Radiology.
• MSD Veterinary Manual, Professional Edition. MSD Veterinary Manual.
• American Veterinary Medical Association Practice Resources. American Veterinary Medical Association.
• WOAH Terrestrial Animal Health Code. WOAH.

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This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.