UTWB Lesson 21: Basic Organs and Structures in the Abdominal and Pelvic Cavity, The Kidneys

When estimating the size of the kidneys in dogs or cats on radiographs, what lumbar vertebrae is used as the reference

L2

Where is the right kidney located in dogs?

Ventral to the last thoracic and first 2-3 lumbar vertebrae

Where is the left kidney located in the dog?

Below the first/second to fourth lumbar vertebrae

Where is the R kidney located in relation to the L kidney in the canine?

R kidney is cranial to the L kidney

Why is the R kidney more restricted in the canine?

Deeply recessed within the caudate lobe of the liver and is related medially to the right adrenal gland and caudal vena cava

What is the clinical consideration of the R kidney in the canine?

More difficult to visualize the R kidney for imaging (radiology) as well as it is more difficult to access for surgery

What does retroperitoneally mean?

Related to the peritoneum of the abdominal cavity

Where are the kidneys located in the canine?

Paired kidneys lie retroperitoneally pressed against the dorsal abdominal wall on either side of the vertebral column

They are usually ventral to the lumbar vertebra and extend cranially under the last ribs

What is the shape of the kidneys in cats and dogs?

Bean shaped

What is present on the kidney surface in cats?

Capsular veins

What is the renal capsule and what does its ability to be easily peeled off mean?

Thin sheet of connective tissue that surrounds the kidney, if there is difficulty peeling off the renal capsule during a necropsy it usually signifies that there was a problem with the kidney

In a healthy kidney, the renal capsule should be easily peeled off

What is the kidney hilus?

Concave indent where the renal artery, vein, and ureter enter the kidney

What are the 2 main internal structures of the kidney, and what are their appearances?

Cortex - granular appearance

Medulla - Striated appearance

Structure of the cortex and medulla in bovine

Cortex is unfused and lobulated

Medulla is also unfused and form medullar projections called renal/medullar pyramids

What does the cortex of the kidney contain?

Renal corpuscles and convoluted parts of the tubules

What does the medulla of the kidney contain?

Contains the collecting ducts

What is the renal crest?

Inner margin of the medulla where the ducts empty into the renal pelvis

What species have medullary pyramids?

pigs, cows, and humans

What are medullar pyramids/papilla?

Medullary zones divided by inter-lobar vessels

What is the renal pelvis?

Wide, funnel-shaped structure that collects the urine, it is the terminal dilated part of the ureter within the kidney

What is the renal/pelvic recess?

Depressions caused by extensions of the renal pelvis into the medulla on both sides of the crest

What is the renal sinus?

fat-filled space surrounding the renal vessels and the ureter

What are the 5 radiographic densities, and what colors do they show up in radiographs?

Air- black

Fat- Lighter black

Soft tissue- Dark gray

Bone- light gray

Metal- white

How are the kidneys viewed on radiographs?

Kidneys are clearly seen in about 50% of plain studies of the abdomen of the dog

Kidneys are more clearly identifiable in cats

What is used to make the kidneys more visible in detailed studies?

Contrast radiography using intravascular perfusion with a contrast agent

What views are usually performed to visualize the kidneys in radiographs?

Lateral and ventral views, R lateral more often than L lateral

What is the normal radiologic appearance of the kidneys?

Bean shaped, smooth, homogenous, soft tissue opacity

Often partially superimposed on one another

What is the normal length of the canine kidney in radiographs?

Appx 2.5-3.5 x the length of the body of the second lumbar vertebra

What is the normal length of the feline kidney in radiographs?

Appx 2.4-3 x the length of the body of the second lumbar vertebra

Where is the R kidney located on radiographs in the dog and cat?

Dog- T13-L2

Cat- L2-L4

Where is the L kidney located on radiographs in the dog and cat?

Dog- L1-3

Cat- L3-L5

What is the normal contrast radiologic appearance of the kidneys?

Both kidneys should be well visualized, with the renal cortices diffusely opaque

Smooth in outline

Medulla should be more radiolucent because of the renal pelvis and pelvis recess

What is anechoic?

Black imaging on ultrasonography correlating to blood/fluid

What is Hypoechoic?

Darker gray imaging on ultrasonography correlating to the renal cortex and liver

What is isoechoic?

Lighter gray than hypoechoic imaging on ultrasonography correlating to fat and the spleen

What is hyperechoic?

White imaging on ultrasonography correlating to bone/gas and connective tissues

Ultrasonography of the kidneys

Echotexture is fine, granular, and markedly hypoechoic

Renal cortex is hypoechoic or isoechoic as compared with the liver

Renal medulla is hypoechoic or anechoic in relation to the renal cortex

What is the corticomedullary junction defined by on ultrasonography?

Presence of bright hyperechoic specks that represent the arcuate vessels

Why is the renal pelvis hyperechoic?

Because of the presence of fat and fibrous tissue

Why does renal length vary in dogs but less in cats?

Because of body size variation

What are some significant features of the bovine kidney?

Lobated

No renal crest or renal pelvis

R kidney is flattened and oval and related ventrally to the colon and descending duodenum

R kidney’s cranial pole embeds in the liver

L kidney slightly twisted and displaced to the right by the rumen

What kidney does this species belong to?

Bovine

What are pyramids drained by in the bovine?

Minor renal calices

What do the minor renal calices drain into in the bovine kidney?

Drained by major calyces (cranial and caudal collecting ducts) that join to form the ureter

How is the ureter structured in regards to calices in the bovine kidney?

The ureter divides into 2 and subsequently into 18-25 calices draining the renal papillae

What do the small ruminant kidneys resemble?

Canine and feline kidneys

Features of small ruminant kidneys

Fusion of the cortex and medullary region

Bean shaped with a renal hilus

Medullary region fuses to form a single renal pyramid/renal crest

Features of the cortex and medulla of the porcine kidney

No external lobation because the cortex is fused and smooth

Internal evidence of lobation

Medullary region comprise separate renal pyramids

Dorsoventrally flattened

What is unique about the porcine kidneys?

Only domestic mammal whose kidneys are at virtually same level (no contact between right kidney and liver)

Internal features of the porcine kidney

up to 10 minor calyces draining same number of medullary pyramids

2 major calyces at both cranial and caudal poles that drain the minor calyces into the renal pelvis

It is multi pyramidal

How is the porcine kidney associated with the pancreas?

Cranial poles of both kidneys associated with the left lobe (left pole) and body (right lobe) of the pancreas

What species does this kidney belong to?

Porcine

What species does this kidney belong to?

Small ruminant

What species do these kidneys belong to?

Equine

Features of the equine R kidney

Retroperitoneal

Heart shaped

Cranial pole makes a renal impression on caudate process of liver

Where is the equine R kidney located?

Ventral to last 2 or 3 ribs and 1st lumbar transverse process

Cranial to the liver

Ventral to the descending duodenum, pancreas, and base of cecum, coils of small colon and small intestine

Medially to the R adrenal gland and aorta

Features of the equine L kidney

More caudal than right kidney

Retroperitoneal (less than R kidney)

Flattened and bean-shaped (number 6)

Where is the equine L kidney located?

Ventral to T17-L2

Cranial to the spleen and stomach

Medial to the aorta and small colon and coils of small intestine

Caudal pole may be just within reach in rectal palpation

Ventrally related to small colon and small intestines

Internal features of the equine kidney

Unipyramidal type with a common renal crest

Renal pelvis

2 polar terminal recesses

Papillary ducts

What is unique about the equine kidney?

Has 2 polar terminal recesses that extend from the poles of the kidneys towards the renal pelvis

Papillary ducts open into the terminal recesses

Where does the kidneys main blood supply come from?

Renal artery

What does the renal artery divide into?

Interlobar arteries

What do interlobar arteries branch into?

Arcuate arteries (reside in the corticomedullary junction)

What do the arcuate arteries give rise to?

Interlobular arteries that radiate to the cortex

What happens after the interlobular arteries?

Afferent arterioles leave the interlobular arteries to enter the renal corpuscles which will divide to form the capillary loop of the glomerulus

What happens after the blood leaves the glomerulus?

The glomerular capillary loops will then recombine to form the efferent arteriole

What does the efferent arteriole do?

Provides a second capillary system which branches into peritubular capillaries that surround the tubules

What species does this kidney belong to?

Canine

What species does this kidney belong to?

Feline