Kidney and Ureter
Anatomy
The kidneys are reddish brown and lie behind the peritoneum high up on the posterior abdominal wall on either side of the vertebral column.
They are largely under cover of the costal margin.
The right kidney lies slightly lower than the left kidney because of the large size of the right lobe of the liver.
On the medial concave border of each kidney is a vertical slit that is bounded by thick lips of renal substance and is called the hilum.
The hilum extends into a large cavity called the renal sinus. The hilum transmits, from the front backward, the renal vein, two branches of the renal artery, the ureter, and the third branch of the renal artery (VAUA).
Lymph vessels and sympathetic fibers also pass through the hilum.
Coverings
- The kidneys have the following coverings:
- Fibrous capsule: This surrounds the kidney and is closely applied to its outer surface.
- Perirenal fat: This covers the fibrous capsule.
- Renal fascia: This is a condensation of connective tissue that lies outside the perirenal fat and encloses the kidneys and suprarenal glands; it is continuous laterally with the fascia transversalis.
- Pararenal fat: This lies external to the renal fascia and is often in large quantity. It forms part of the retroperitoneal fat.
- The perirenal fat, renal fascia, and pararenal fat support the kidneys and hold them in position on the posterior abdominal wall.
Renal Structure
- Each kidney has a dark brown outer cortex and a light brown inner medulla.
- The medulla is composed of about a dozen renal pyramids, each having its base oriented toward the cortex and its apex, the renal papilla, projecting medially.
- The cortex extends into the medulla between adjacent pyramids as the renal columns. Extending from the bases of the renal pyramids into the cortex are striations known as medullary rays.
- The renal sinus, which is the space within the hilum, contains the upper expanded end of the ureter, the renal pelvis. This divides into two or three major calyces, each of which divides into two or three minor calyces. Each minor calyx is indented by the apex of the renal pyramid, the renal papilla.
Anterior and posterior relation of kidneys
Right Kidney
Anteriorly: The suprarenal gland, the liver, the second part of the duodenum, and the right colic flexure
Posteriorly: The diaphragm; the costodiaphragmatic recess of the pleura; the 12th rib; and the psoas, quadratus lumborum, and transversus abdominis muscles. The subcostal (T12), iliohypogastric, and ilioinguinal nerves (L1) run downward and laterally.
Left Kidney
Anteriorly: The suprarenal gland, the spleen, the stomach, the pancreas, the left colic flexure, and coils of jejunum
Posteriorly: The diaphragm; the costodiaphragmatic recess of the pleura; the 11th (the left kidney is higher) and 12th ribs; and the psoas, quadratus lumborum, and transversus abdominis muscles. The subcostal (T12), iliohypogastric, and ilioinguinal nerves (L1) run downward and laterally.
Blood Supply
Arteries
- The renal artery arises from the aorta at the level of the second lumbar vertebra.
- Each renal artery usually divides into five segmental arteries that enter the hilum of the kidney. They are distributed to different segments or areas of the kidney.
- Lobar arteries arise from each segmental artery, one for each renal pyramid. Before entering the renal substance, each lobar artery gives off two or three interlobar arteries. The interlobar arteries run toward the cortex on each side of the renal pyramid.
- At the junction of the cortex and the medulla, the interlobar arteries give off the arcuate arteries, which arch over the bases of the pyramids. The arcuate arteries give off several interlobular arteries that ascend in the cortex. The afferent glomerular arterioles arise as branches of the interlobular arteries.
Blood Supply
Veins
- The renal vein emerges from the hilum in front of the renal artery and drains into the inferior vena cava.
Lymph Drainage
- Lymph drains to the lateral aortic lymph nodes around the origin of the renal artery.
Nerve Supply
- The nerve supply is the renal sympathetic plexus. The afferent fibers that travel through the renal plexus enter the spinal cord in the 10th, 11th, and 12th thoracic nerves.
Ureter
Location and Description
- The two ureters are muscular tubes that extend from the kidneys to the posterior surface of the urinary bladder.
- The urine is propelled along the ureter by peristaltic contractions of the muscle coat, assisted by the filtration pressure of the glomeruli.
- Each ureter measures about 10 in. (25 cm) long and resembles the esophagus (also 10 in. long) in having three constrictions along its course:
- where the renal pelvis joins the ureter,
- where it is kinked as it crosses the pelvic brim, and
- where it pierces the bladder wall
- The renal pelvis is the funnel-shaped expanded upper end of the ureter.
- It lies within the hilum of the kidney and receives the major calyces.
- The ureter emerges from the hilum of the kidney and runs vertically downward behind the parietal peritoneum (adherent to it) on the psoas muscle, which separates it from the tips of the transverse processes of the lumbar vertebrae.
- It enters the pelvis by crossing the bifurcation of the common iliac artery in front of the sacroiliac joint. The ureter then runs down the lateral wall of the pelvis to the region of the ischial spine and turns forward to enter the lateral angle of the bladder.
Relations
Right Ureter
Anteriorly: The duodenum, the terminal part of the ileum, the right colic and ileocolic vessels, the right testicular or ovarian vessels, and the root of the mesentery of the small intestine
Posteriorly: The right psoas muscle, which separates it from the lumbar transverse processes, and the bifurcation of the right common iliac artery
Left ureter
Anteriorly: The sigmoid colon and sigmoid mesocolon, the left colic vessels, and the left testicular or ovarian vessels
Posteriorly: The left psoas muscle, which separates it from the lumbar transverse processes, and the bifurcation of the left common iliac artery
The inferior mesenteric vein lies along the medial side of the left ureter
Blood Supply
Arteries
- The arterial supply to the ureter are:
- upper end, the renal artery;
- middle portion, the testicular or ovarian artery; and
- in the pelvis, the superior vesical artery.
Veins
- Venous blood drains into veins that correspond to the arteries.
Lymph Drainage
- The lymph drains to the lateral aortic nodes and the iliac nodes.
- Nerve Supply
- The nerve supply is the renal, testicular (or ovarian), and hypogastric plexuses (in the pelvis). Afferent fibers travel with the sympathetic nerves and enter the spinal cord in the first and second lumbar segments.
Congenital Abnormalities of the Kidney
Renal agenesis
- Renal ectopia
- Pelvic kidney
- Horseshoe kidney
- Crossed dystopia
- Infantile polycystic disease
- Unilateral multicystic dysplastic kidney
Aberrant renal vessels
- Multiple renal arteries and veins
Duplication
- Duplex kidney
- Duplex renal pelvis
- Duplex kidney and ureter
Others
- Congenital hydronephrosis
- Retrocaval ureter
- Congenital megaureter
Renal agenesis
- Bilateral agenesis
- Ultrasound: oligohydramnios
- Potter facies:flattened nose, low-set ears, and recessed chin
- Talipes equinovarus
- Pulmonary hypoplasia
- Incompatible with life
- Unilateral agenesis
- The remaining kidney undergoes compensatory hypertrophy
- Patients often have adequate renal function
- May develop progressive glomerular sclerosis
Horseshoe Kidney
- When the caudal ends of both kidneys fuse as they develop, the result is horseshoe kidney.
- Both kidneys commence to ascend from the pelvis, but the interconnecting bridge becomes trapped behind the inferior mesenteric artery so that the kidneys come to rest in the low lumbar region.
- Both ureters are kinked as they pass inferiorly over the bridge of renal tissue, producing urinary stasis, which may result in infection and stone formation. Surgical division of the bridge corrects the condition
Horseshoe Kidney
Clinical features
- Presents as a fixed, nonmobile, firm mass in the midline at the level of lower lumbar region.
- There may be urinary stasis with consequent infection and nephrolithiasis
Investigations
- It is diagnosed radiologically.
- Urogram shows the lower pole calyces on both sides being directed towards the midline.
Treatment
- Whatever the complication occurs, it is treated accordingly.
- Separation of isthmus is not indicated, unless to approach aorta for aortic diseases.
Autosomal recessive polycystic kidney disease
Also known as childhood polycystic kidney disease
Clinical features
Rare autosomal recessive disease
Presents in infancy with progressive and often fatal renal failure
c. Gross
Bilaterally enlarged kidneys
Multiple small cysts in the cortex and medulla
The cysts are oriented in a radial fashion with their long axis at right angles to the capsule
May also have multiple hepatic cysts and congenital hepatic fibrosis
Autosomal recessive polycystic kidney disease
Autosomal dominant polycystic kidney disease
Also known as adult polycystic kidney disease
Genetics
- Autosomal dominant inheritance
- Mutation of PKDl gene on chromosome 16
- The PKDl gene produces a transmembrane protein called polycystin 1
Other mutations involvePKD2 and PKD3 genes
Clinical features
- Asymptomatic with normal renal function until middle age
- Presents with renal insufficiency,hematuria, and hypertension
- Abdominal masses and flank pain
- Most patients develop end-stage renal failure by their seventh decade
- Diagnosis: ultrasound and CT scans
Massive bilateral kidney enlargement with large bulging cysts
Cysts are filled with serous, turbid, or hemorrhagic fluid
Micro: functioning nephrons are present between the cysts
Extrarenal manifestations
Liver cysts
Berry aneurysms of the circle of Willis
Mitral valve prolapse
Colonic diverticula
