Kidney and suprarenal anatomy

Position and hilum

• Retroperitoneal on the posterior abdominal wall, from about T12 to L3. The right kidney is 1–2 cm lower because of the liver. Each moves 2–3 cm with breathing.
• The hilum is at about L1 (transpyloric plane), about 5 cm from the midline. From front to back: renal vein, renal artery, renal pelvis; arterial branches may also pass behind the pelvis.

Coverings (inside out)

Retroperitoneal fibrosis: a plaque of fibrous tissue around the infrarenal aorta pulls both ureters towards the midline (medial deviation) and obstructs them: back pain, high ESR, bilateral hydronephrosis, rising creatinine. Enlarged lymph nodes push ureters laterally instead.

Relations

• Areas touching the kidney directly, without peritoneum: suprarenal, duodenum and colon on the right; suprarenal, pancreas with splenic vessels and colon on the left. The liver, stomach, spleen and jejunum are separated by peritoneum.
• The pleura lies behind the upper pole: a posterior approach or biopsy can cause pneumothorax.
• The duodenum is at risk in right nephrectomy; the spleen, pancreatic tail and colon in left nephrectomy.

Internal structure

• Cortex outside; medulla of 8–18 pyramids whose apices (papillae) open into minor calyces. Renal columns of cortex dip down between pyramids. Medullary rays are straight bundles of collecting ducts and straight tubules running up from the medulla into the cortex.
• Arterial sequence: renal, segmental (end-arteries), interlobar (in the renal columns), arcuate (arching along the bases of the pyramids at the corticomedullary junction), interlobular (cortical radiate), afferent arterioles, glomeruli, efferent arterioles, peritubular capillaries and vasa recta (the countercurrent exchangers of the medulla).
• Because segmental arteries are end-arteries, occlusion causes a wedge-shaped infarct. The PCT and thick ascending limb are most vulnerable to ischaemia (acute tubular necrosis).

Renal vessels

• Renal arteries leave the aorta at L1–L2; the right is longer and passes behind the IVC. Accessory renal arteries (about 25–30%) may cross and obstruct the pelviureteric junction.
• Renal artery stenosis: in older smokers with vascular disease, atheroma at the ostium or proximal 2 cm; in young women, fibromuscular dysplasia in the distal two-thirds. Clues: resistant hypertension, flash pulmonary oedema, an asymmetric small kidney, a flank bruit, and a sharp creatinine rise after an ACE inhibitor (which removes angiotensin II support of efferent tone).
• Renal veins go to the IVC. The left renal vein is longer, crosses in front of the aorta just below the SMA (nutcracker compression), and receives the left gonadal and left suprarenal veins. The right gonadal vein enters the IVC directly. So left varicoceles are common, and a new left varicocele in an older man suggests a renal tumour in the left renal vein.
• The abdominal aortic aneurysm is usually infrarenal; rupture gives back pain, hypotension and a pulsatile mass.

Ureter

• About 25 cm, retroperitoneal, running down on psoas major along the tips of the lumbar transverse processes, crossing the bifurcation of the common iliac artery at the pelvic brim, then down the lateral pelvic wall to enter the bladder obliquely (the oblique tunnel acts as an anti-reflux valve).
• In men the vas deferens crosses above the ureter; in women the uterine artery crosses above it about 1.5–2 cm lateral to the cervix, the danger point in hysterectomy ("water under the bridge").
• At operation the ureter is told from vessels and nerves by its peristalsis (vermiculation) when gently pinched; injuries are commonest in hysterectomy and colorectal surgery.

• Blood supply is segmental (renal, gonadal, aorta, common and internal iliac, vesical). Vessels come from the medial side in the abdomen and the lateral side in the pelvis; preserve the adventitia.
• Ureteric colic (T11–L2) radiates loin to groin. As the stone descends, pain refers to the front of the upper thigh and the scrotum or labium through the genitofemoral nerve (L1–L2), which runs on psoas next to the ureter.
• Duplex kidney comes from an early split (bifid ureter) or a double ureteric bud. By the Weigert–Meyer rule the upper-pole ureter opens lower and more medially; in a girl it may open below the bladder neck (urethra or vagina), giving constant dribbling despite normal voiding. The lower-pole ureter tends to reflux.

Stones linked to anatomy and gut disease

Suprarenal (adrenal) glands

• Right: pyramidal, behind the IVC, on the upper pole. Left: crescentic, on the medial border above the hilum, behind the stomach and pancreas.
• Arteries from three sources: superior from the inferior phrenic, middle from the aorta, inferior from the renal artery.
• Single vein: right into the IVC directly (very short, easily torn at right adrenalectomy); left into the left renal vein.
• Cortex (mesoderm): glomerulosa (aldosterone, controlled mainly by angiotensin II and K⁺), fasciculata (cortisol), reticularis (androgens). The fetal cortex makes DHEA-S for placental oestriol. Medulla (neural crest): chromaffin cells with preganglionic sympathetic supply.
• After bilateral adrenalectomy, lifelong hydrocortisone and fludrocortisone are needed; after unilateral removal the other gland suffices.

Congenital anomalies

• Horseshoe kidney: lower poles fuse, ascent is stopped by the inferior mesenteric artery; Turner syndrome; obstruction, stones, infection.
• Wilms tumour: large smooth flank mass in a young child, arising within the kidney (claw sign), not crossing the midline, normal catecholamines; linked to WAGR (aniridia). Do not biopsy through the flank before staging.

Remember Hilum front to back: vein, artery, pelvis; ureter narrowest at the vesicoureteric junction.

Exam trap The uterine artery crosses above the ureter near the cervix: the danger point in hysterectomy.

Exam trap The left gonadal and suprarenal veins drain into the left renal vein; the right ones go straight to the IVC.

How FCPS asks about this

• Nerve carrying lower ureteric stone pain to the groin and thigh: genitofemoral nerve.
• Arteries along the bases of the pyramids: arcuate arteries; medullary rays are collecting ducts running up into the cortex.
• Structure touching the left kidney without peritoneum between: body and tail of the pancreas (with splenic vessels).
• Duplex kidney cause and ectopic upper-pole ureter symptom: split or double ureteric bud; constant dribbling plus normal voiding.
• How to recognise the ureter at surgery: peristalsis when pinched.
• Ureters drawn medially around a normal aorta with high ESR: retroperitoneal fibrosis.
• Adrenal veins and arteries: right vein to IVC, left to left renal vein; arteries from inferior phrenic, aorta and renal.