The upper retroperitoneal organs share Gerota's fascia and a common surgical approach. This tab covers the kidneys (position, fascial spaces, hilum, internal structure, vasculature, imaging), the ureters (course, blood supply, endoscopic anatomy), and the adrenals (relations, highly variable vasculature, and cortical/medullary histology).
Kidneys
Position and Relations
- Dimensions — each kidney is 10–12 cm long, 5.5–7.5 cm wide, 2.5–3 cm thick; the male kidney weighs ≈125–170 g (the female 10–15 g less). Children show fetal lobulations (gone by age 1), and a dromedary hump (left > right) is a normal parenchymal bulge.
- Level (supine, end-expiration) — the right kidney sits 1–2 cm lower than the left (liver), from L1 to L3 with its upper pole at the 12th rib; the left runs T12–L3 with its upper pole at the 11th rib. Both hila lie at ≈L1. The longitudinal axes are oblique — upper poles more medial/posterior, lower poles lateral/anterior ("Lower LANTern") — with the medial aspect rotated ~30° anteriorly.
- Pleura — its inferior limit lies between the 10th and 12th ribs. Percutaneous access above the 11th rib (10th interspace) risks the pleura and lung, so prefer subcostal or 11th-interspace access. The hepatorenal and splenorenal ligaments tether the upper poles — excessive downward traction can tear the liver or splenic capsule.
Perirenal Space and Gerota Fascia
- The perirenal space contains the adrenal, kidney, ureter, perirenal fat, renal pedicle, and gonadal vessels; perirenal fat is finer and paler than the coarse pararenal fat. The space is cone-shaped, open inferiorly into the extraperitoneal pelvis.
- Gerota (renal) fascia encloses it — closed superiorly and laterally, open inferiorly. The anterior and posterior laminae merge laterally as the lateroconal fascia (separating the anterior and posterior pararenal spaces), which fuses with the peritoneum at the white line of Toldt. Clinical: perinephric fluid can track down into the pelvis without breaching Gerota's. The fascia also envelops the aorta and IVC and extends along the ureter as periureteral fascia.
Renal Hilum
Structures from anterior to posterior: renal Vein, renal Artery, renal pelvis/Ureter, and the posterior segmental Artery. To reach the right hilum, mobilise the 2nd duodenum and pancreatic head medially to expose the IVC; for the left, mobilise the pancreatic tail and spleen.
Internal Structure
The medulla holds 8–18 striated pyramids, each ending in a papilla cupped by a minor calyx; minor calyces join into major calyces, then the renal pelvis. The cortex (~1 cm) covers the pyramid bases and dips between them as the columns of Bertin. The calyces, pelvis, ureters, bladder, and urethra are lined by transitional epithelium (urothelium).
Vasculature
- Arterial cascade: main renal artery → anterior/posterior branch → segmental → lobar → interlobar → arcuate → interlobular → afferent arteriole → glomerulus → efferent arteriole.
- The anterior branch supplies ~2/3 of the kidney (apical, upper, middle, lower segmental arteries); the posterior branch becomes the posterior segmental artery (the first, most consistent branch). Segmental arteries are end arteries — occlusion causes segmental infarction. The avascular line of Brödel (between anterior and posterior territories, just posterolateral) is the preferred plane of incision. Accessory renal arteries occur in ~25–28% and may contraindicate laparoscopic donor nephrectomy.
- Venous drainage has extensive collaterals (unlike the arteries). The right renal vein is short (2–4 cm) with no tributaries; the left is long (6–10 cm) and receives the left adrenal, left gonadal, and often a lumbar vein. The left renal vein crosses between the SMA and aorta — compression there causes nutcracker syndrome.
- Pelvicalyceal system — usually 3 upper-pole calyces, 3–4 interpolar, and 2–3 lower-pole; the renal pelvis holds 3–10 mL.
Imaging
On ultrasound the cortex and pyramids are hypoechoic to the liver/spleen, with echogenicity rising with disease. CT is homogeneous unenhanced, and CT angiography is the gold standard for the renal arteries. On MRI, the cortex is brighter than the medulla on T1 and slightly less intense on T2.
Ureters
Course and Relations
The ureter (22–30 cm, 1.5–6 mm) arises from the ureteric bud of the mesonephric (Wolffian) duct at week 5 (the bud forms the collecting system; the metanephric blastema forms the nephrons). It runs along the psoas, with three radiologic constrictions: the ureteropelvic junction, the iliac-vessel crossing, and the ureterovesical junction. Intraoperatively it is found at the bifurcation of the common iliac artery. The gonadal vessels cross anterior to it ("water under the bridge"). In women it runs under the ovarian artery, medial to the uterine artery, through the cardinal ligament near the cervix.
Vasculature
Blood supply is medial in the abdomen and lateral in the pelvis: the proximal ureter from renal-artery branches (medially), the middle from the aorta/common iliac (posteriorly), and the distal from the superior/inferior vesical arteries (laterally) — about 10% of women carry much of the distal supply via the uterine artery, which is divided at hysterectomy. Accordingly, an endoureterotomy is cut posterolaterally (proximal), anteriorly (mid), and medially (distal). Handle the ureter gently — stripping its adventitia causes ischaemia and stricture.
Endoscopic Anatomy
Both orifices are rarely seen at once; a higher-grade (0–4) orifice is more lateral. The intramural ureter is the narrowest segment (3–4 mm). In duplex systems, the Weigert-Meyer rule states the upper-pole ureter inserts inferiorly and medially to the lower-pole ureter.
Adrenals
Relations
Both glands sit at the 11th/12th rib level within Gerota's fascia, the right more superior than the left, each weighing ≈5 g (no gender difference). The right gland is triangular (bordered by liver anterolaterally, duodenum anteromedially, IVC medially, psoas posteriorly); the left is crescentic (splenic vessels and pancreatic body anteriorly, aorta medially, psoas posteriorly). Both abut the diaphragmatic crus.
Vasculature
Arterial and venous anatomy is highly variable and redundant (an adrenal artery is identified in only ~1% of laparoscopic adrenalectomies). Three arterial sources: the superior adrenal artery (from the inferior phrenic — constant), the middle (from the aorta — variable), and the inferior (from the renal artery — variable). Venous drainage is by a single central vein: the right adrenal vein is short and drains into the IVC; the left is longer and drains into the left renal vein (with the inferior phrenic vein). Lymph drains right → paracaval, left → para-aortic.
Histology and Hormones
A sympathetic exception governs innervation: pre-ganglionic fibres (T11–L2) synapse directly on the medullary chromaffin cells (no post-ganglionic neuron), while post-ganglionic fibres supply the cortex. The gland has two embryologic parts:
- Cortex (~90% of mass; intermediate mesoderm) — three layers: zona glomerulosa (~15%, aldosterone), zona fasciculata (~80%, cortisol/glucocorticoids), and zona reticularis (~5–7%, sex steroids — DHEA, DHEA-S, androstenedione). "GFR → salt, sugar, sex." The sex steroids are the largest output by mass (>20 mg/day) but least important for adult homeostasis.
- Medulla (neural crest → chromaffin cells) — secretes the catecholamines epinephrine (80%), norepinephrine (19%), dopamine (1%) from tyrosine. The adrenal is the primary source of systemic epinephrine, and PNMT (which converts norepinephrine to epinephrine) is nearly unique to it (driven by the high-glucocorticoid cortical blood reaching the medulla).
Imaging
CT is the most widely used modality — normal adrenal tissue (including adenoma) is ≤10 Hounsfield units unenhanced. MRI offers superior contrast resolution, and US helps distinguish solid from cystic lesions.
Self-Test
1. What is the typical arterial supply to the adrenal glands? Superior adrenal artery (from the inferior phrenic), middle adrenal artery (from the aorta), and inferior adrenal artery (from the renal artery).
2. Where do the adrenal veins drain? Right adrenal vein → IVC; left adrenal vein → left renal vein.
3. What are the three zones of the adrenal cortex and what do they secrete? Zona glomerulosa → aldosterone; zona fasciculata → cortisol; zona reticularis → sex hormones.
4. Describe the autonomic innervation of the adrenal medulla. Pre-ganglionic sympathetic fibres act directly on the medulla — there are no post-ganglionic fibres.
5. Which enzyme converts norepinephrine to epinephrine? PNMT (phenylethanolamine-N-methyltransferase).
6. What catecholamines does the medulla produce, and from which amino acid? Dopamine, norepinephrine, and epinephrine — all synthesised from tyrosine.