Comparative Anatomy of the Mammalian Kidney

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

Key Takeaways

• Mammalian kidney structure exhibits significant species-specific variation in lobation, medullary thickness, and vascular arrangement, directly impacting renal function, diagnostic interpretation, and disease susceptibility. Ruminants, for example, possess a multilobar kidney with distinct lobes and papillae, contrasting with the unilobar structure of dogs, cats, and horses.
• Renal concentrating ability is intrinsically linked to nephron architecture, specifically the proportion and length of juxtamedullary nephron loops and relative medullary thickness. Cats, with their high medullary thickness, exhibit superior urine concentrating capacity compared to ruminants and pigs, influencing the interpretation of urine specific gravity values in clinical assessment.
• Topographic differences in kidney position across species (e.g., right kidney more cranial in horses and cattle than in dogs and cats) dictate clinical examination techniques, imaging approaches, and surgical access, necessitating species-specific diagnostic strategies.
• Clinical assessment of renal function requires species-matched reference intervals for parameters like urine specific gravity and serum creatinine, as absolute values can be misleading due to variations in muscle mass (creatinine) and baseline concentrating ability (urine specific gravity).
• Iatrogenic complications during renal biopsy, such as hemorrhage, are influenced by species-specific renal vascularity and anatomical positioning; for instance, the equine kidney's larger size and vascularity increase hemorrhage risk compared to smaller domestic species.
• Misinterpretation of normal anatomical features, such as the lobulated kidney in cattle and pigs, as pathological findings (e.g., infarction or dysplasia) is a common error, underscoring the importance of understanding species-specific gross morphology for accurate diagnosis.

The mammalian kidney performs the same core tasks across species, yet its structural solutions vary considerably. This article compares renal anatomy across domestic mammals, with attention to lobation, nephron architecture, vascular arrangement, and concentrating capacity. It serves veterinary students who need a working framework for interpreting species differences in renal function, diagnostic imaging, and susceptibility to renal disease. The focus is on dogs, cats, horses, ruminants, and pigs, with selected reference to laboratory and exotic species where the comparison clarifies a principle.

Understanding these differences matters clinically. A drug dosing interval that suits the dog may not suit the horse, and a renal biopsy finding in a cow must be interpreted against bovine renal architecture, not canine. The comparative approach also explains why some species concentrate urine far better than others and why certain nephrotoxins produce species-specific lesion patterns.

At a Glance

Gross Morphology and Lobation

The kidney develops as a metanephric structure with a lobulated external surface in early fetal life. In most domestic species the lobes fuse during development, producing a smooth external surface with a single renal pyramid and a renal crest. The dog, cat, horse, and pig retain this unilobar arrangement. The ox and other ruminants retain the fetal lobation, so the adult kidney shows distinct lobes separated by deep fissures, each lobe with its own medullary pyramid and papilla projecting into a calyx.

The bovine kidney is the classic multilobar example. Its papillae open into calyces that drain into the renal pelvis, and there is no renal crest. The small ruminant kidney is smoother than the bovine kidney but still shows partial lobation, with a single papilla in sheep and goats. The pig kidney is unilobar with a well-developed renal crest, but its medulla is divided into multiple pyramids that project into the pelvis, giving the cut surface a lobed appearance that can be mistaken for true lobation.

The right kidney lies more cranial than the left in most domestic mammals, fitting into the renal fossa of the liver. In the dog and cat the right kidney is firmly attached to the body wall and the left is more mobile. The horse has a flattened right kidney and a bean-shaped left kidney, both lying beneath the last ribs. In pigs the kidneys are more symmetric in position, and in cattle the right kidney is lobulated and elongated, the left more irregular and pendulous. In marmosets, a New World monkey used in comparative research, the right kidney typically sits at the L1-L2 level and the left between L2 and L3, with the kidneys at the same level in roughly a third of individuals, a pattern that resembles the pig more than the dog. Morphometric and skeletopy data for marmoset kidneys

Nephron Architecture

All mammalian kidneys contain cortical and juxtamedullary nephrons. The distinction rests on the length of the loop of Henle and the position of the glomerulus. Cortical nephrons have short loops that dip only into the outer medulla. Juxtamedullary nephrons have long loops that descend deep into the inner medulla, and it is these nephrons that establish the osmotic gradient necessary for urine concentration.

The proportion of juxtamedullary nephrons and the length of their loops correlate with concentrating ability. The cat has a high relative medullary thickness and a well-developed inner medulla, consistent with its ability to produce highly concentrated urine. The dog has a moderate medullary thickness. The horse, despite being a herbivore, has a relatively well-developed medulla and can concentrate urine effectively when water is restricted. Ruminants and pigs have shorter loops and lower concentrating capacity, though the camel and other desert-adapted mammals exceed all domestic species in this regard.

The renal corpuscle itself is similar across species, with a glomerular tuft supplied by an afferent arteriole and drained by an efferent arteriole. The efferent arteriole of juxtamedullary nephrons gives rise to the vasa recta, the hairpin capillary loops that run alongside the loops of Henle and participate in countercurrent exchange. The arrangement of these vessels is essential to the medullary osmotic gradient. The historical recognition of the glomerulus as the site of urine formation dates to Marcello Malpighi, whose seventeenth century drawings of renal glomeruli, described as minimae glandulae, established the structural basis for renal filtration. Malpighi's original drawings of renal glomeruli

Renal Vasculature and Innervation

The renal artery divides into interlobar arteries that course between the renal lobes or pyramids. In unilobar species these vessels run toward the corticomedullary junction, where they form arcuate arteries. Interlobular arteries branch from the arcuate arteries and ascend through the cortex, giving off afferent arterioles along the way. The venous drainage follows a parallel course, with interlobular veins draining into arcuate veins and then into interlobar veins that converge to form the renal vein.

The horse is notable for a large renal artery that divides early into several branches entering the hilus separately. The bovine kidney has multiple interlobar arteries, one for each lobe, which enter along the medial border instead of through a single hilus. This arrangement complicates surgical approaches to the bovine kidney and explains why renal biopsy in cattle carries a higher risk of hemorrhage than in dogs.

The kidney receives sympathetic innervation from the renal plexus, with vasoconstrictor fibers supplying the renal vasculature. Parasympathetic innervation is sparse. The juxtaglomerular apparatus, located at the vascular pole of each glomerulus, contains granular cells that secrete renin in response to reduced renal perfusion pressure, sympathetic stimulation, and decreased distal tubular sodium delivery. This apparatus is structurally similar across domestic mammals, though the density of renin-containing cells varies with species and physiologic state.

Species Differences in Renal Topography

The position of the kidneys relative to the vertebral column and abdominal organs influences clinical examination, imaging, and surgical access. In the dog, the right kidney lies at the level of the T13 to L3 vertebrae, the left at L2 to L4. The cat shows a similar arrangement, with the right kidney more cranial and fixed, the left more caudal and mobile. The horse has the right kidney at T16 to L2 and the left at T18 to L2, both largely retroperitoneal and difficult to palpate per rectum. The bovine right kidney extends from T12 to L3, the left from L2 to L5, and the left kidney is the one most often palpable per rectum in cattle.

These topographic differences have practical consequences. Ultrasound windows differ, with the dog and cat allowing easy imaging from a lateral approach and the horse requiring a transrectal or transabdominal approach. Renal biopsy in the horse is typically performed transrectally or with ultrasound guidance through the right body wall. In cattle, biopsy of the left kidney can be performed percutaneously from the right side because the left kidney is displaced to the right by the rumen. MSD Veterinary Manual clinical resources

Applied Renal Assessment Across Species

Clinical Examination and Localization

The clinical approach to renal disease begins with localization, and species differences in renal topography directly shape the physical examination. In dogs and cats, the right kidney sits within the renal fossa of the caudate liver lobe, making it palpable in most patients, while the left kidney is more mobile and often palpable caudally. In horses, the right kidney lies entirely beneath the ribs and the left kidney is partially covered by the spleen, so neither is reliably palpable per rectum or through the body wall. Ruminants have a lobulated right kidney that is not palpable externally, the left kidney in cattle is suspended on a long mesentery and may be palpated per rectum, where its lobulated surface and mobility are distinctive. Small ruminants and pigs follow the general pattern of a non-palpable retroperitoneal kidney in most adult animals.

When a patient presents with suspected renal disease, the sequence begins with serum biochemistry, specifically urea and creatinine, followed by urinalysis with sediment examination. Neither urea nor creatinine is a sensitive early marker of dysfunction because both rise only after substantial nephron loss. Urine specific gravity must be interpreted against the species baseline. Dogs and cats normally concentrate urine above 1.030 and 1.035 respectively, horses above 1.020, and cattle above 1.015. A fixed specific gravity in the isosthenuric range with azotaemia indicates renal failure instead of prerenal or postrenal causes. The concentrating ability of each species reflects its nephron architecture and medullary organization, so the same specific gravity value carries different diagnostic weight in a horse versus a cat.

Ultrasonography provides the next diagnostic layer. The equine kidney is best imaged transabdominally from the right paralumbar fossa for the right kidney and the left flank for the left kidney. In cattle, transrectal ultrasonography of the left kidney is practical and allows assessment of the lobulated contour. In dogs and cats, standard transthoracic and transabdominal approaches are well established. Renal length correlates with body weight in dogs, and published reference intervals exist for each breed group. A kidney that is enlarged with a thickened cortex suggests acute nephritis or lymphoma, while a small irregular kidney with loss of corticomedullary distinction indicates chronic disease.

Imaging and Functional Assessment

Advanced imaging has expanded the comparative assessment of renal structure. Computed tomography and magnetic resonance imaging provide detailed morphometry and vascular anatomy, and these modalities have been applied to species as small as marmosets, where the kidneys are bean-shaped, smooth, and located between the first and third lumbar vertebrae Dünkel-Duarte et al., morphometry and skeletopy of kidneys in marmoset. The same imaging principles translate across domestic mammals, though the equipment and anesthetic requirements differ substantially. A horse requires a large-bore CT or standing sedation with a specialised table, while a cat can be imaged in a standard veterinary CT unit.

Functional imaging with radionuclide techniques, including scintigraphy using technetium-labelled tracers, allows assessment of glomerular filtration and tubular function without invasive sampling. These methods have been validated in laboratory species and are used clinically in dogs and cats for split renal function assessment before nephrectomy. The choice of tracer depends on the question: glomerular filtration rate is measured with agents cleared by filtration alone, while tubular secretion can be assessed with tracers that undergo active tubular transport. In production animals, scintigraphy is rarely practical due to facility requirements and radiation safety constraints, so functional assessment relies on endogenous creatinine clearance, which requires timed urine collection and is cumbersome in cattle and horses.

Nephron Type and Concentrating Capacity

The mammalian kidney contains two nephron populations: superficial cortical nephrons with short loops of Henle and juxtamedullary nephrons with long loops that extend deep into the medulla. The proportion of juxtamedullary nephrons and the relative medullary thickness determine maximum urine concentrating ability. The dog and cat have a high proportion of long-looped nephrons and a thick medulla, supporting their ability to produce highly concentrated urine. The horse has a moderately thick medulla and produces urine that is less concentrated than that of carnivores but more concentrated than that of most herbivores. Cattle and sheep have a lower medullary thickness and produce dilute urine relative to carnivores, which suits their high-water-turnover grazing physiology. The pig has a relatively simple kidney with a low concentrating capacity, consistent with its omnivorous diet and ready access to water.

These differences have direct clinical consequences. A cat that cannot concentrate urine above 1.020 has lost a substantial fraction of its renal functional reserve, whereas a cow with the same specific gravity may still have normal renal function. Fluid therapy plans must account for these differences. A dehydrated horse requires larger volumes of isotonic fluids than a dog of similar body weight because the horse's renal concentrating ability is lower and its daily water turnover is higher. Conversely, a cat in chronic kidney disease may benefit from a diet that reduces renal solute load, a strategy that is less relevant in herbivores.

Comparative Renal Pathology and Biopsy

Renal biopsy is indicated when imaging and laboratory findings do not establish a diagnosis, particularly when immune-mediated glomerular disease, neoplasia, or infiltrative disease is suspected. The approach varies by species. In dogs and cats, ultrasound-guided percutaneous biopsy with a spring-loaded needle is standard. In horses, percutaneous biopsy is performed from the right paralumbar fossa with ultrasound guidance, and the risk of hemorrhage is higher because the equine kidney is larger and more vascular. In cattle, biopsy is rarely performed antemortem because the lobulated kidney is difficult to access and the clinical value is limited by the cost of the procedure relative to the animal's value.

The biopsy sample must contain both cortex and medulla to assess the full nephron. A sample that contains only medulla is non-diagnostic for glomerular disease. The pathologist should be informed of the species, because the normal histology differs. The equine kidney has a thicker interstitium than the canine kidney, and the bovine kidney has prominent interlobular septa that can be mistaken for fibrosis by an inexperienced observer. The glomerular basement membrane thickness also varies, with the horse having a thicker basement membrane than the dog.

Monitoring and Documentation

Serial monitoring of renal disease requires consistent parameters. Body weight, urine output, serum creatinine, and urine specific gravity form the core dataset. In hospitalized patients, urine output should be measured with a urinary catheter in dogs and cats when acute kidney injury is suspected. In horses, urine output is difficult to measure accurately without a catheter, and clinical assessment of hydration, including skin turgor, mucous membrane moisture, and capillary refill time, becomes more important. In cattle, urine output can be estimated from the frequency and volume of urination, but this is imprecise.

The following table summarizes the monitoring parameters and their clinical significance across species.

Documentation should include the imaging findings, biopsy results if obtained, and the trend of serial laboratory values. The comparative anatomy of the kidney informs every step of this assessment, from the initial palpation to the interpretation of a specific gravity value. A clinician who understands the nephron architecture and medullary organization of each species can interpret laboratory and imaging findings with appropriate context. The historical foundation of renal anatomy, from Malpighi's first descriptions of glomeruli as minimae glandulae to modern imaging, underscores that structural knowledge remains the basis of clinical reasoning Nicosia and Cassoli, Malpighi's forgotten drawings of renal glomeruli.

Recognized Complications and Early Detection

The most consequential failure mode in comparative renal assessment is extrapolating a diagnostic threshold from one species to another. A serum creatinine concentration that signals advanced disease in a dog may reflect normal muscle mass in a horse, while the same value in a cat can coexist with substantial functional reserve loss. Early detection depends on species-specific reference intervals and serial trend analysis instead of single-point comparisons. Urine specific gravity interpretation carries the same risk. A value of 1.020 in a dog indicates concentrating impairment, yet in a pig or camelid it may fall within expected variation. The discriminating check is always the species-matched reference range, not the absolute number.

A second recognized complication is the misclassification of lobation as pathology. The multi-lobed kidney of cattle and pigs, with its distinct renculi and deep fissures, is frequently mistaken for renal infarction, chronic pyelonephritis, or congenital dysplasia on ultrasound. The bovine kidney's external lobation is normal anatomy, and the same applies to the pig. The discriminating feature is the smooth, organized arrangement of lobules with uniform corticomedullary definition, whereas infarction produces wedge-shaped echolucencies that cross lobar boundaries. The MSD Veterinary Manual professional edition provides species-specific imaging guidance that clarifies these distinctions.

Iatrogenic injury during renal biopsy represents a third failure mode. The equine kidney lies retroperitoneal and deeply recessed, making blind percutaneous biopsy hazardous. The feline kidney is more mobile and superficially positioned, but its smaller size increases the risk of sampling the medulla or renal pelvis instead of cortex. Early detection of biopsy complications relies on post-procedure monitoring for hematuria, perirenal fluid accumulation on ultrasound, and serial packed cell volume measurement. The NCBI Bookshelf veterinary and comparative biomedical sciences collection contains comparative anatomical references that inform safe approach planning.

Common Errors and Corrective Action

Less experienced clinicians frequently assume that nephron type predicts gross morphology. The assumption that a unipapillary kidney implies a simple, unbranched pelvis is correct for dogs and cats, but the horse, despite its unipapillary gross structure, possesses a renal pelvis with extensive recesses that extend deep into the parenchyma. Corrective action is to review the species-specific pelvic architecture before interpreting contrast studies or planning surgery.

A second common error involves the cranial pole of the right kidney. In dogs and cats, the right kidney sits within the renal fossa of the caudate liver lobe, and its cranial pole is often invisible on ultrasonography due to acoustic shadowing from the liver. Students frequently report the kidney as absent or small. The corrective action is to use a flank or intercostal window and to recognize that the left kidney, being more caudal and mobile, is the reliable ultrasonographic landmark.

A third error is the assumption that renal vascular anatomy is uniform. The horse has a single renal artery per kidney, whereas cattle frequently have multiple segmental arteries. The pig's renal artery divides early into dorsal and ventral branches. Corrective action before nephrectomy or renal transplantation studies is to consult species-specific vascular descriptions, such as those provided in the marmoset renal morphometry and vascularisation study, which demonstrates how vascular patterns vary even within a single genus.

Limitations of Current Evidence

Comparative renal anatomy across domestic mammals rests on a surprisingly narrow evidence base. Much of the foundational description derives from historical anatomical texts instead of modern imaging-confirmed studies. The historical drawings of renal glomeruli by Malpighi remind us that the microscopic architecture was described centuries ago, yet quantitative comparative data on nephron dimensions, glomerular density, and loop of Henle length across species remain incomplete.

Expert opinion still differs on the functional significance of the bovine and porcine lobulated kidney. Some authorities regard lobation as a mechanical adaptation that resists compression within the abdominal cavity, while others consider it a developmental remnant without functional consequence. The evidence does not yet resolve this question. Similarly, the extent to which the horse's pelvic recesses contribute to countercurrent concentration is debated, with some texts describing them as minor extensions and others attributing significant concentrating capacity to them.

The use of pigs as models for human renal physiology has generated useful comparative data, particularly regarding postnatal renal maturation, as summarized in the piglet pediatric surrogate review. However, extrapolation from pigs to other domestic species is limited by differences in body size, diet, and renal architecture. The clinician should treat cross-species physiological extrapolation with caution.

Referral and Escalation Criteria

Referral to a specialist is warranted when renal disease is suspected but the diagnosis remains uncertain after basic assessment, when imaging findings are ambiguous, or when the planned intervention carries significant risk. A horse with unexplained hematuria and normal bladder ultrasound should be referred for endoscopic evaluation. A cat with suspected renal lymphoma requires ultrasonography and biopsy under specialist guidance. A dog with suspected congenital renal dysplasia should be referred for genetic testing and histopathology.

Laboratory involvement extends beyond routine biochemistry. Urine protein-to-creatinine ratio, symmetric dimethylarginine, and fractional excretion studies require laboratory validation for the species in question. The AVMA practice resources provide guidance on appropriate sample handling and laboratory quality standards.

Regulatory reporting applies in specific circumstances. Suspected adverse reactions to renally eliminated drugs, particularly non-steroidal anti-inflammatory drugs in dehydrated patients, may require reporting to pharmacovigilance programs. In production animals, renal disease associated with feed contamination or environmental toxins may trigger reporting obligations under WOAH terrestrial animal health standards. The clinician should know the reporting requirements of their jurisdiction.

Frequently Asked Questions

How Do I Choose Between Ultrasound-Guided and Blind Percutaneous Renal Biopsy in a Small Animal Patient?

Ultrasound guidance is preferred whenever available because it permits real-time visualization of the kidney, reduces the risk of penetrating the renal pelvis or major vessels, and allows sampling of the cortical rim instead of the medulla. Blind biopsy is reserved for settings where imaging is unavailable or the patient is too unstable for prolonged positioning. In cats and small dogs, the smaller renal size increases the risk of capsular laceration and hemorrhage, so a 18 gauge or smaller needle is advised. Consult a current interventional radiology or soft tissue surgery reference for needle selection and patient preparation. Coagulation status should be assessed before biopsy in all species.

What Are the Practical Alternatives When Advanced Imaging Is Not Available for Renal Assessment?

When computed tomography or magnetic resonance imaging is unavailable, a structured combination of survey radiography, abdominal ultrasonography, and serum biochemistry provides most of the diagnostic information needed. Survey radiographs identify renomegaly, nephrolithiasis, and asymmetry in size. Ultrasonography assesses cortical echogenicity, corticomedullary junction distinction, pelvic dilation, and cystic lesions. Doppler interrogation of renal arterial flow can be performed on most modern ultrasound machines. Urinalysis with sediment examination and urine protein-to-creatinine ratio adds functional information. In horses, rectal palpation of the left kidney remains a useful adjunct. These modalities together usually distinguish chronic kidney disease from acute injury, obstruction, or neoplasia.

How Does Renal Concentrating Ability Differ Between a Horse and a Dog, and Why Does This Matter Clinically?

Horses produce urine with a lower maximum osmolality than dogs, typically in the range of 1200 to 1400 mOsm/kg compared with up to 2500 mOsm/kg in dogs. This reflects the horse's lower medullary interstitial solute gradient and its evolutionary reliance on high-volume, dilute urine. Clinically, this means a horse can become dehydrated despite producing apparently adequate urine volumes. Urine specific gravity in a dehydrated horse may only reach 1.035 to 1.040, whereas a dehydrated dog should concentrate above 1.030 readily. When assessing renal function in horses, serum creatinine and symmetric dimethylarginine are more reliable than urine specific gravity alone. The piglet kidney shows closer functional resemblance to the human infant kidney, which is relevant when extrapolating pediatric pharmacokinetic data across species.

What Documentation Is Required When Managing a Patient With Suspected Renal Disease in a Mixed Practice Setting?

Record the signalment, presenting complaint, physical examination findings, and a problem list. Document baseline body weight, body condition score, blood pressure, and urine specific gravity. Record all laboratory results with reference intervals for the species and laboratory used. Note the imaging findings and the reason for any deviation from the standard diagnostic pathway. If a biopsy is performed, document the number of cores, needle gauge, ultrasound guidance used, and any complications. Serial measurements of body weight, urine output, and renal biochemical parameters should be logged with timestamps. This documentation supports monitoring of disease progression and provides a defensible record if the case is referred or audited.

How Should I Explain Renal Disease and Its Prognosis to an Owner of a Senior Cat?

Use plain language that distinguishes chronic kidney disease from acute kidney injury. Explain that the kidneys filter waste products and regulate water balance, and that in chronic disease, nephrons are progressively lost. Describe the diagnostic findings in terms the owner can understand, such as diluted urine, elevated kidney enzymes, and changes on ultrasound. Discuss the expected clinical course, including the possibility of stable disease for months to years with appropriate management. Be honest about the limitations of treatment and the signs that indicate declining quality of life. Provide written information and a clear plan for monitoring, including when to return for repeat blood work and blood pressure measurement. Encourage the owner to contact the clinic early if vomiting, inappetence, or lethargy develops.

When Should I Refer a Renal Case to a Specialist, and What Information Should Accompany the Referral?

Refer when there is diagnostic uncertainty, when the patient fails to respond to initial therapy, when advanced imaging or biopsy is required, or when the owner requests a second opinion. Cases with suspected renal neoplasia, complex urolithiasis, or acute anuric kidney injury warrant early referral. Include a summary of the history, physical examination findings, serial laboratory results, blood pressure measurements, imaging reports, and the treatments administered with response to each. Provide the owner with a copy of the records and a list of current medications. If the patient is unstable, stabilize hydration and electrolyte abnormalities before transport. Contact the receiving clinician directly to discuss the case and confirm that they can accept the patient.

Related Clinical & Scientific Guides

• Canine Respiratory System: Anatomy and Physiology
• Feline Cardiopulmonary Physiology: Heart-Lung Interactions
• Equine Ocular Anatomy: Adnexa and Globe Structures

References and Further Reading

• Malpighi's Forgotten Drawings of Renal Glomeruli.. 2025.
• The Potential Use of Piglets as Human Pediatric Surrogate for Preclinical Pharmacokinetic and Pharmacodynamic Drug Testing.. 2016.
• Radionuclide, magnetic resonance and computed tomography imaging in European round back slugs (Arionidae) and leopard slugs (Limacidae).. 2021.
• Morphometry and skeletopy of kidneys and renal vessels in marmoset (Callithrix spp.).. 2024.
• NCBI Bookshelf: Veterinary and Comparative Biomedical Sciences. NCBI Bookshelf.
• MSD Veterinary Manual, Professional Edition. MSD Veterinary Manual.
• American Veterinary Medical Association Practice Resources. American Veterinary Medical Association.
• WOAH Terrestrial Animal Health Code. WOAH.

Related Articles

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• Comparative Anatomy of the Mammalian Ear: Canine, Feline, Equine
• Comparative Anatomy of the Ruminant and Equine Stomach
• Comparative Anatomy of the Avian Respiratory System
• Comparative Anatomy of the Avian Skeleton: Flight and Locomotion

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.