Cow kidney anatomy

Cow kidney anatomy refers the description of its external and internal features. It is considered the main organ of the cow’s urinary system.

However, a cow’s urinary system consists of two kidneys: right and left. Here, I will present the unique anatomical features of these kidneys with hand-drawn diagrams and real pictures.

Quick answer: Cow kidney anatomy has unique external features in shape, surfaces, and extremities, but shares common internal features.

First, I will help you differentiate the cow’s right kidney from the left. Then I will describe these kidneys in the cow’s urinary system in an easy way.

How many kidneys does a cow have?

Figure 1 shows a hand-drawn diagram of the cow’s urinary system, highlighting the kidneys. It shows that a cow has two kidneys (right and left).

However, each kidney is superficially divided into several polygonal lobes by external fissures. The number of polygonal lobes varies (16-20), and the fissures are filled with fat (Figure 2).

Thus, the lobulation on the external surface of the cow/cattle/bovine kidneys is different from that of the horse, dog, and goat kidneys.

Both the right and left kidneys of a cow are red-brown. However, the cow’s left kidney is heavier than the right.

Table 1 shows the average measurements (cm) of the right and left kidneys of a cow –

Mesurements	Right  kidney of the cow	Left kidney of the cow
Length	15 – 17 centimeters	13 – 17 centimeters
Width	8.5 – 10 centimeters	7.5 – 8.5 centimeters
Thickness	5 centimeters	7.5 centimeters
Weight	625 – 650 grams	675 – 700 grams

How to identify or differentiate between a cow’s right and left kidneys?

The cow’s right and left kidneys have basic structural similarities, except for their external appearance. In my view, you can identify a cow’s right and left kidneys at first glance if you try.

However, this knowledge might help you describe these two kidneys perfectly. I suggest that you learn to differentiate the two kidneys in the cow’s urinary system using samples in practice.

Let’s try to differentiate the cow’s right and left kidneys using Figure 3. It highlights the main external features that differentiate the two kidneys.

Both kidneys present well-identified polygonal lobes on their external surfaces. However, the outline of these right and left kidneys is variable.

• One shows an elongated elliptical outline (Kidney 1 from Figure 3), and
• Another shows an elongated outline but is slightly shorter than the first (Kidney 2 from Figure 3).

The figure also shows that one kidney is dorsoventrally flattened and has two identifiable surfaces. In contrast, the other kidney has three identifiable surfaces.

This is the basic way to differentiate the cow’s right kidney from the left. Here, kidney 1 from Figure 3 is the cow’s right kidney, and kidney 2 is the left kidney.

However, you will find more differentiating external anatomical features in their extremities and hilus. Table 2 shows the 3 main differentiating features between the right and left kidneys –

Features	Cow’s right kidney	Cow’s left kidney
Surfaces	Two	Three
Cranial extremity	Thick	Rounded
Hilus	Dorsally	Ventrally

To understand the positions and specific surfaces of the right and left kidneys, you can learn their detailed anatomy.

Cow kidney anatomy

Figure 4 shows an overview of the anatomy of the cow’s kidneys. It highlights the unique external and internal anatomical features of the right and left kidneys.

However, to describe the cow’s kidney anatomy, you might mention the following –

• Location: The cow’s right and left kidneys are located on either side of its vertebral column, with little variation in their extension.
• Surfaces and borders: Because of their location, the right and left kidneys present asymmetrical surfaces and borders.
• Extremities: Both the right and left kidneys of a cow present two extremities: cranial and caudal. However, the appearance of these extremities varies between the cow’s right and left kidneys.
• Location of the hilus: The cow’s right and left kidneys also have variable hilus positioning.
• Fixation: Various structures help these kidneys remain fixed in position.
• Internal structures of the kidney: It includes the capsule and cavity of each kidney. Again, the kidney cavity comprises the calyces (major and minor), renal pyramids, and renal sinus.

Now, I will describe every feature of the cow’s kidney with the diagrams. This might be a good guide to the cow’s kidney anatomy that you can follow for your exam preparation.

Where are the kidneys located in a cow?

Figure 5 highlights the location of the cow’s right and left kidneys. I made this figure on the cow’s kidneys with both a hand-drawn diagram and real pictures.

Both the right and left kidneys are located in the upper cranial part of the abdominal cavity and above the peritoneum. Thus, these cow’s kidneys are also known as the retroperitoneal organs.

However, the cow’s right and left kidneys are embedded in a large amount of perirenal fat termed the adipose capsule. Thus, the presence of external fat (as well as internal fat) is normal for ruminant/bovine/cattle/cow kidneys.

Location of the right kidney: According to the figure, the cow’s right kidney is located below the proximal end of the last rib and two or three lumbar transverse processes.

Left kidney location: The figure also shows that the location of the cow’s left kidney depends on stomach fullness.

When the rumen (part of the stomach) is full: It pushes the cow’s left kidney caudally and across the median plane of the body. Thus, the left kidney lies on the right side, just caudal and slightly ventral to the left kidney.

However, the cow’s left kidney lies ventral to the bodies of the 3rd to 5th lumbar vertebrae.

When the rumen is not so full: Here, the left kidney remains at the same level but partly to the left of the median plane.

Anatomy of the cow’s right kidney

Figure 6 presents the external anatomical features of the cow’s right kidney. It has an elongated elliptical outline and is flattened dorsoventrally.

Thus, the right kidney of a cow presents two surfaces, two borders, and two extremities –

• Surfaces: They include the dorsal and ventral surfaces
• Borders: They are the medial and lateral borders
• Extremities: They include the cranial and caudal extremities.

Surfaces, borders, and extremities of the right kidney

Surfaces: Here, Figure 6 shows that the dorsal surface of the cow’s right kidney is rounded and nearly convex. However, this surface remains in contact with the sublumbar muscle of the cow’s muscular system.

Again, the ventral surface of the cow’s right kidney is less convex than the dorsal surface. It remains in contact with the cow’s liver, pancreas, small intestine (especially the duodenum), and parts of the colon.

Borders: The medial border of the cow’s right kidney is straight. It lies parallel to the cow’s caudal vena cava and aorta.

However, the lateral border of this right kidney is slightly convex (Figure 6).

Extremities: Figure 6 presents the thick cranial extremity of the cow’s right kidney. It lies in the renal impression of the cow’s liver and remains in contact with the right adrenal body.

However, the caudal extremity of the right kidney is free, narrow, and pointed.

Hilus of the cow’s right kidney

Hilus: First, let’s learn the features of the hilus of the cow’s kidney. This is a concave area of the bovine kidney where some structures enter and others exit.

• Arteries and nerves enter through the hilus of the kidney.
• Structures or organs exit through the hilus of the kidneys: ureter, veins, and lymphatic vessels.

Now, I will show you the hilus of the cow’s right kidney. This is very important for the practical positioning of the cow’s right kidney.

Figure 7 highlights the hilus of the cow’s right kidney. It shows that the hilus is located at the cranial part of the ventral surface of the medial border of the right kidney.

How to memorize the features of the cow’s right kidney?

Memorizing the features of the cow’s right kidney is simple once you understand its structures. Generally, a summary of its surfaces, borders, extremities, and hilus will help you memorize the cow’s right kidney.  

Table 3 summarizes the external anatomical features of the cow’s right kidney –

External features	Cow’s right kidney
Surfaces	Dorsal – concave Ventral – less convex
Borders	Medial – straight Lateral – convex
Extremities	Cranial – rounded and thick Caudal – narrow and pointed
Hilus	Cranial part of the ventral surface + near medial border

You need to follow similar strategies to memorize the features of the cow’s left kidney.

Cow’s left kidney anatomy

Figure 8 presents an overview of the anatomy of the left kidney of a cow. This left kidney is also elongated but is three-sided.

Thus, the cow’s left kidney presents three surfaces, three borders, and two extremities –

Surfaces	Borders	Extremities
Dorsal (convex)Ventral (flat)Ruminal (flat)	Medial (convex)Lateral (slightly convex)Ventral (convex)	Cranial Caudal

Surfaces, borders, and extremities of the bovine/cattle’s left kidney

Surfaces: According to Figure 8, the dorsal surface of the cattle’s left kidney is convex. However, the ventral surface is nearly flat and remains in contact with the intestine of the cow’s digestive system.

Again, the ruminal surface is exceptional in the left kidney of the large ruminant (cattle/cow/ox/buffalo). Here in the cow’s left kidney, this ruminal surface is more or less flattened. However, it lies in contact with the parietal surface of the rumen.

Borders: The dorsal and ventral surfaces of the left kidney meet medially and form the medial border. This border is convex at its cranial part and concave at the caudal part.

However, the lateral border of the left kidney is between the ruminal and dorsal surfaces. Here, the lateral border is slightly convex in the left kidney.

The ventral border is also convex and is between the ruminal and ventral surfaces. Figure 8 also highlights all three borders of the ruminant’s kidney.

Extremities: Figure 8 also shows that the cranial extremity of the left kidney is small and rounded. However, the caudal extremity of this kidney is large and rounded.

These features help you position the left kidney of a cow accurately.

Where is the hilus of the bovine’s left kidney?

Figure 9 presents the unique arrangement of the hilus of the bovine’s left kidney. This type of hilus is found only in the left kidneys of large ruminants such as cattle, cows, oxen, and buffalo.

Here, the dorsal surface of the kidney presents an oblique depression (lateral to medial aspect). Within this depression, the hilus is located on its cranio-lateral aspect.

However, the hilus of the bovine/cow’s left kidney opens laterally at the oblique depression. The position of the hilus of the cow’s left kidney is a unique identifying feature compared to other species.

In this hilus, you will find the renal artery, veins, nerves, lymphatics, and fat. But I will help you identify the more grossly visible structures in this hilus.

Here, the renal artery is elastic and dorsally positioned (Figure 10). Again, the wall of the renal vein is thin and in a middle position.

However, the cow’s ureter is a muscular structure whose lumen appears star-shaped.  This ureter lies just ventral to the renal artery and vein (Figures 9 and 10).

However, a thick layer of fat surrounds the artery, vein, and ureter in the hilus.

Differences between the hilus of the right and left kidneys: In the cow’s right kidney, the hilus is an extensive elliptical cavity. However, in the cow’s left kidney, it is a deep, elongated fissure.

How do the cow’s kidneys remain fixed in their positions?

Different factors and structures are responsible for keeping the cow’s kidneys in their positions –

• The renal artery, veins, and ureter attach to the hilus of the kidney and primarily help hold it in place.
• A large amount of renal fat and renal fascia keeps the kidneys in place.
• However, pressure from adjacent organs like the liver, pancreas, and caecum strongly keeps the kidneys in place.

Here, the renal fascia forms from a condensation of the extraperitoneal connective tissue around the kidneys. However, it continues laterally with the fascia transversalis of the cow’s abdominal muscles. 

Internal structures of the cow’s kidneys

Figure 11 shows an overview of the internal features of the cow’s kidneys. It consists of the outer capsule and internal cavity.

What features should you identify and describe from the internal aspect of the kidney? Well, the following are internal structures you need to identify and describe perfectly –

• Capsules: The outer covering of the kidneys.
• Cortex and medulla section along with corticomedullary junction
• Renal pyramid with renal papillae
• Calyces system: Includes the major and minor calyces
• Hilus with renal sinus
• Large quantity of fat within the internal structures

Now, I will help you learn the above-mentioned internal features of the cow’s kidney one by one. Make sure you can identify these features of the kidney with the help of Figure 11.

Capsule of the bovine kidneys

A thin but strong capsule of fibrous tissue covers each cow’s kidney. It continues along the wall of the renal sinus and reflects as the tubular structure around the calyces.

However, this fibrous capsule may easily separate from the parenchyma of a healthy cow’s kidney.

Features of the internal cavity of the kidney

A longitudinal section of a cow’s kidney shows that it consists of an external cortical and internal medullary substances. Here, Figure 12 highlights the external cortical (cortex) and internal medullary substances (medulla) of the cow’s kidney.

Cortex: The cortex consists of a reddish-brown layer and has a granular appearance. However, it shows many minute dark structures known as the renal Malpighian corpuscles.

These corpuscles are the dilated origins of the renal tubules and contain a tuft of capillaries (glomerulus). However, these features are clearly visible in the microscopic image of the cow’s kidneys.

Medulla: It is pale and, at its junction with the cortex, has an intermediate vascular zone (corticomedullary junction). However, it is pyramid-shaped and thus known as the renal pyramid.

There are about 17 – 20 renal pyramids in the cow’s kidney structure. Again, the bases of these pyramids point towards the cortex.

Part of the cortex dips inward, forming the renal columns. However, each renal pyramid has medullary rays that form the renal papilla at its apex. 

Minor and major calyces of the cow’s kidneys

Figure 13 is a hand-drawn diagram highlighting the minor and major calyces of the cow’s kidney. This well-developed calyx system is also a key feature of large ruminants like cows, oxen, and buffalo.

Here, the renal papilla is enclosed by the small funnel-shaped end of the tube. This tube is termed the minor calyx of the kidney.

Several minor calyces from the cranial and caudal aspect unite to form the major calyces. A cow’s kidney has mainly two (sometimes three) major calyces.

Two such major calyces from two extremities of the cow’s kidney unite at the hilus to form the renal sinus. From the renal sinus arises the excretory duct, or the cow’s ureter.  

In the cow, the renal sinus remains filled with fat. However, the calyces, sinus, and large intrarenal vessels also remain embedded in this fat.

FAQ’s on the cow’s kidney anatomy

Conclusion

Thus, cow kidney anatomy comprises descriptions of the external and internal features. Here, the external features are the shape, lobulation, surfaces, borders, extremities, and location of the hilus for each kidney.

However, internal features include structures from the capsule to the renal sinus. Again, the specific location and fixation of the cow’s two kidneys are also important for a complete anatomical description.

References

• Ghosh, R. K.: Primary Veterinary Anatomy, 2nd Ed.Current Books International, Kolkata.
• Sabreen M Al-Janabi. Morphohistological study of kidney in local cow (Bos taurus) in the Middle of Iraq. Zool Entomol Lett 2024;4(2):92-96.  
• Rowen D. Frandson, W. Lee Wilke, and A. Dee: Anatomy and physiology of farm animals, 4^th edn.Wiley-Blackwell, USA.
• Carvalho, F. S. et al. (2009). External gross anatomy of the bovine kidney, Cells, tissues, organs, 190(1), 53–58.
• Getty, R. Sission and Grossman’s The anatomy of the domestic animals, 5^th Edn. W. B. Saunders and Co., Philadelphia (USA).
• Francismar S. et al., The Bovine Kidney as an Experimental Model in Urology: External Gross Anatomy. Cells Tissues Organs 1 June 2009; 190 (1): 53–58.   
• Nickel, R., Schummer, A. and Seiferle, E.: The anatomy of domestic animals, 1^st Edn. Verlag Paul Parey, Berlin.
• Yagana Bukar Majama, Gross Anatomy and Histology of the Urinary System of the Spur-Winged Goose (Plectropterus Gambensis). 2024. VETERINARIA 73 (1): 53-61.
• Hermanson et al., Miller and Evan’s Anatomy of the Dog, 5^th Edn. Elsevier.
• Hailat, N. Q. et al. (2023). Pathological and molecular study of kidneys in apparently healthy cattle, Veterinary World, 16(12), 2488–2496.
• McLeod, W. N.: Bovine anatomy, 2^nd Edn. Burgess Publishing Co., Minneapolis.
• Kadhim, A. B. et al. (2023). Anatomical study of the kidney of the camel. Iraqi Journal of Veterinary Sciences, 37(I-IV), 73-79. 
• Dyce, K. M., W. O. Sack, and CSG Wensing: Textbook of Veterinary Anatomy, Lea & Febiger. Philadelphia
• Braun U. (1991). Ultrasonography of the right kidney in cows. American journal of veterinary research, 52(12), 1933–1939.

Written by