Kidney, Ureter Anatomy and Posterior Abdominal Wall

• The anatomy of the kidney and ureter is the subject
• Learning outcomes include understanding the anatomy of the kidney, adrenal gland, and surrounding tissues.
• Describe the anatomy of the ureters, innervation and blood supply.
• Understand the main congenital abnormalities that may occur in the renal system like horseshoe kidney, vesico-ureteric reflux, duplex ureter.
• The topics include urinary calculi, and radiological imaging.

Posterior Abdominal Wall

• The osteology includes five lumbar vertebrae, sacrum, pelvic bones, and ribs (11-12).
• Muscles include psoas major and minor, quadratus lumborum, and iliacus.

Transpyloric Plane

• Passes through L1, found at 1/2 way from the suprasternal notch to the symphysis pubis (1/2 way from xiphoid to umbilicus).
• The linea semilunaris cuts the costal margin at the 9th costal cartilage at this level.
• The fundus of the gallbladder, pylorus of stomach, first part of duodenum, neck of pancreas, portal vein formation(can happen between L1-L2), and the superior mesenteric artery origin are all found at the transpyloric plane.
• Hila of kidneys (L higher than R).
• Hilum of the spleen can also be found at the transpyloric plane.

Nerves of the Posterior Abdominal Wall

• The Lumbar plexus is formed by the anterior rami of L1-3 (L4) and receives contribution from T12.
• Lateral to the psoas are the subcostal nerve (T12), the ilio-hypogastric nerve (L1), the ilio-inguinal nerve (L1), the lateral cutaneous nerve of the thigh (L2-3), and the femoral nerve (L2-4)
• Medial to psoas are the obturator nerve (L2-4) and the lumbosacral trunk (L4-5).
• Through the psoas runs the genitofemoral nerve (L1-2).

Surface Anatomy and Position of Kidneys

• Bean-shaped and retroperitoneal in the posterior abdominal region, lateral to the vertebral column.
• Kidneys extend from approximately T12 vertebra to L3 vertebra.
• The right kidney sits lower than the left.
• The hilum of each kidney is located around L1.

Anterior Relations

• The right kidney is near the right adrenal gland, liver, peritoneum, the right colic flexure, and the duodenum.
• The left kidney is near the left adrenal gland, stomach, spleen, pancreas, left colic flexure, and the descending colon.

Posterior Relations

• The quadratus lumborum and transversus abdominis make up the muscles of the posterior abdominal wall.
• The left kidney is near the 11th and 12th rib.
• The right kidney is near the 12th rib.
• Subcostal vessels and nerves and also the iliohypogastric and ilioinguinal nerves are located in the posterior relations.

Diaphragm

• Posterior to the superior pole of the kidneys.
• The pleural sacs and the costodiaphragmatic recesses, extend posterior to the kidneys
• Biopsies may cause pneumothorax.

Fascia of the Kidney

• The renal capsule is adhered to the kidney surface itself.
• It prevents the spread of infections to the surrounding regions.
• Adipose capsule: cushions the kidney and assists in attaching it to the body wall.
• Immediately outside the renal capsule the perinephric fat completely surrounds the kidney.
• Posterior and posterolateral to each kidney sits the paranephric fat.
• Renal (Gerota’s) fascia is a dense fibrous connective tissue that serves to anchor the kidney.
• It is also important for determining the stage of renal cancer.
• Suprarenal Glands are also enclosed in this fascial compartment, separated from the kidneys by a thin septum usually.

Internal Anatomy of the Kidney

• Renal cortex is a band of pale tissue that surrounds the renal medulla, extends between pyramids and forms renal columns.
• The renal medulla is the inner portion of the kidney, divided into triangular-shaped tissue - the renal pyramids.
• The bases directed outward and the apices project inward.
• The apical projection is known as the renal papilla and contains the openings of the papillary ducts, surrounded by a minor calyx.
• Minor calyxes receive urine from the papillary ducts
• Major calyxes refer to the unification of several minor calices.
• Renal pelvis: funnel-shaped superior end of the ureters formed by the unification of 2-3 major calices.

Hilum of the Kidney

• A deep vertical slit on the medial margin found in each kidney.
• Entry and exit point for renal vessels, lymphatics, and nerves.
• The vein lies Anterior.
• The artery lies Middle.
• The Ureter lies Posterior.
• Renal arteries (L1-L2).
• Left renal artery usually arises a little higher than the right.
• The right artery is longer and passes posterior to the IVC.
• Renal veins exist.
• Left renal vein is longer, passes between the abdominal aorta and SMA.

Renal Arteries

• Each one divides into anterior and posterior branches.
• These branches are end arteries.
• They do not form anastomoses.
• Trauma or obstruction in one arterial branch can lead to ischaemia and necrosis of the renal parenchyma supplied by this vessel.

Ureters

• Muscular tubes that transport urine from kidneys to the bladder.
• Starts at the renal pelvis; carries urine from the renal pelvis to the bladder.
• Descends inferiorly and medially at around ~30cm.
• The renal pelvis narrows as it passes inferiorly through the hilum of the kidney and becomes continuous with the ureter at the ureteropelvic junction.
• Ureters descend retroperitoneally on the medial aspect of the psoas major muscle and along the tips of transverse processes of L1-L5 vertebrae.
• At the pelvic brim, the ureters cross either the end of the common iliac artery or the beginning of the external iliac artery and then enter the pelvic cavity.
• They enter the bladder at the level of the ischial spine.

Ureter Relations

• In males, the ureter is crossed by the vas deferens.
• In females the ureter is crossed by the uterine artery.

Ureters Constrictions

• At the ureteropelvic junction is the first constriction.
• Where the ureters cross the pelvic brim, is the second constriction.
• Where the ureters enter the wall of the bladder, is the third constriction.

Ureters: Blood, Histology, Innervation

• The renal, gonadal, common iliac arteries, the internal iliac artery and its branches, and the abdominal aorta provide the blood supply.
• Transitional Epithelium (Waterproof and Distensible) makes up the histology.
• Innervation stems from the renal, aortic, superior hypogastric, and inferior hypogastric plexuses (nerves follow blood supply).
• Visceral efferents are both sympathetic and parasympathetic.
• Visceral afferents return to the spinal cord level at T11 to L2.
• Pain is referred to cutaneous areas supplied by T11 to L2 (posterior and lateral abdominal wall and genitals, ‘loin to groin’ pain).

Ureteric Calculi (Kidney Stones)

• Ureters can be identified along the tips of L1-L5 TV processes and the sacroiliac joint on the x-ray.
• Most kidney stones or urinary calculi are calcium oxalate +/- phosphate.
• These should appear on a plain X-Ray film.
• Other kidney stone types include Urate, Cystine, and Struvite (NH4, PO4, Mg).
• These stone types might not appear on a plain X-Ray film.

Vesico-Ureteric Reflux

• The retrograde flow of urine from the bladder to the ureter or kidney.
• Primarily congenital (most common), the intramural region of the ureter is too short and there is no valve effect.
• Secondary to high pressure voiding states, posterior urethral valves, or from neuropathic bladder (stimulus to voiding doesn’t work properly), duplex collecting system.
• Reflux is associated with recurrent UTIs.

Hydronephrosis

• Distention and dilatation of the renal pelvis & calyces.

Causes of Reflux

• Aberrant renal artery that is crossing over the ureteropelvic junction.
• Stones and enlarged prostate.
• Pregnancy and cancer of the cervix can cause reflux.

Bifid Collecting System in the Ureters

• Increase in complexity caused by upper pole obstruction, calculi, and reflux disease.
• The Weigert-Meyer Rule applies to duplex collecting systems.
• When there is complete, duplicated ureters insert separately into the bladder.
• The upper pole ureter is the ectopic ureter, and it's orifice inserts inferomedially in the bladder in relation to the lower pole normal ureter.

Kidney Defects

• Kidney defects included pelvic kidney, horseshoe kidney, and duplex collecting ducts.

Adrenal Glands

• Lie immediately superior and anterior to the superior pole of each kidney.
• Functionally unrelated to the kidneys.
• Surrounded by perinephric fat and enclosed by renal fascia.
• Outer cortex and inner medulla structures.
• The cortex is regulated by the pituitary, hypothalamus, and renin-angiotensin Axis.
• Clinical examples: Cushing’s Syndrome, Conn’s Disease, and Addison’s Disease
• Medulla: Contains chromaffin cells to produce adrenaline and noradrenaline (catecholamines).
  • Clinical examples: Phaeochromocytoma and Waterhouse Friderichsen.

Adrenal glands: Relations and positions

• The coeliac trunk and left crus of the diaphragm both medially relate to the left adrenal gland.
• The medial kidney aspect and upper pole along renal hilum laterally relate.
• The lesser sac and stomach are anterior.
• The diaphragm is positioned posteriorly.
• Inferior vena cava medially lies relative to the right adrenal gland.
• The upper renal pole laterally lies relative to the right adrenal gland.
• The bare area of the liver anteriorly positions relative to the right adrenal gland.
• Posterior to the right arena gland is the diaphragm.

Adrenal Glands Blood Supply

• The three main sources of adrenal gland blood are the superior suprarenal arteries, the middle suprarenal artery, and the inferior suprarenal arteries.
  • Superior suprarenal arteries come via the inferior phrenic artery
  • Middle suprarenal artery, directly from the ab. aorta
  • Inferior suprarenal arteries are via the renal artery
• The blood's venous drainage is supplied by the suprarenal vein.
• The right suprarenal vein is short and drains directly into the IVC.
• The left suprarenal vein drains into the left renal vein.

Lymphatic Drainage

• Lymphatic drainage of the kidney goes to the lumbar nodes around the origin of the renal artery.
• The upper ureter drains to lumbar nodes.
• The middle ureter drains to common iliac nodes.
• The inferior ureter drains to external and internal iliac nodes.