Renal Sinus

sinus renalis

The renal sinus is the central cavity of the kidney that opens to the outside at the hilum. It contains the renal pelvis, the calyces, branches of the renal vessels and nerves, all cushioned in fat. The kidney tissue wraps around it like a shell.

Anatomical Data

Structure & Supply

Location	Central cavity of the kidney, opening medially at the hilum
Parts	Renal pelvis Major and minor calyces Segmental renal vessels Renal nerves Lymphatics Sinus fat
Nerve Supply	Renal plexus
Blood Supply	Segmental branches of the renal artery
Venous drainage	Renal vein tributaries
Lymphatic drainage	Lateral aortic (lumbar) nodes

Biomechanics

Function & Actions

Houses and protects the collecting system and the vessels entering and leaving the kidney.

Clinical Relevance

Clinical Notes

Fat in the renal sinus increases with age and obesity and shows up as a bright central echo on ultrasound. Small fluid-filled cysts next to the pelvis (parapelvic cysts) can mimic hydronephrosis on imaging. Tumours that invade the sinus fat carry a higher stage in kidney cancer.

Pathology

Common Injuries & Conditions

Parapelvic Cyst

A benign fluid-filled sac within the renal sinus, usually harmless but occasionally pressing on the collecting system.

Renal Sinus Lipomatosis

Excessive build-up of fat in the sinus, often with ageing, obesity or kidney atrophy.

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