Posterior Relations of the Kidney — Surgical Importance

Overview of Posterior Relations

Why Each Structure is Surgically Important

1. Diaphragm

• The upper pole of each kidney lies behind the diaphragm.
• During posterior or loin approach surgery (e.g., nephrectomy), the pleura may be inadvertently breached, causing a pneumothorax.
• Intercostal access above the 12th rib (required for upper-pole access in PCNL or partial nephrectomy) risks the posterior pleural reflection, which lies at the level of the 11th–12th rib.
• "Part of either kidney will lie above the eleventh/twelfth rib, especially the left kidney, and upper pole access may require an intercostal entry, placing the intercostal artery or pleura at risk." — Grainger & Allison's Diagnostic Radiology

2. 12th Rib (and 11th Rib for left kidney)

• The ribs form the posterosuperior boundary. The left kidney is in contact with both the 11th and 12th ribs; the right kidney only with the 12th.
• Surgical incisions (loin or posterior approach) are made along or below the 12th rib to access the kidney.
• A subcostal incision below the 12th rib avoids the pleura.
• Resection of the 12th rib gives wider access but requires careful pleural protection.

3. Subcostal Nerve (T12)

• Runs behind the kidney, just below the 12th rib.
• At risk of damage during posterior surgical approaches, causing denervation of the anterior abdominal wall muscles, leading to a visible bulge (pseudohernia) in the flank postoperatively.
• Must be identified and protected during loin incisions.

4. Iliohypogastric (L1) and Ilioinguinal (L1) Nerves

• These emerge from the lateral border of psoas major and course behind the lower pole.
• Injury during loin or flank dissection can cause sensory loss over the groin, scrotum/labia, and upper medial thigh, or contribute to post-surgical groin pain.

5. Psoas Major Muscle

• The medial part of the posterior surface of each kidney lies on the psoas muscle.
• When the kidney is adherent to psoas (e.g., due to fibrosis, perinephric infection), psoas fascia may be included in the dissection — this is a recognised manoeuvre in difficult nephrectomies.
• The psoas also guides the approach during retroperitoneoscopic surgery.

6. Quadratus Lumborum and Lumbodorsal (Thoracolumbar) Fascia

• The lateral posterior surface of the kidney rests on quadratus lumborum.
• The lumbodorsal fascia covers these posterior muscles and is a key anatomical layer in posterior/retroperitoneal surgical access.
• A lumbodorsal incision allows the kidney to be reached without incising muscle, reducing morbidity — a key advantage of the posterior retroperitoneal approach.
• The transversalis fascia fuses with the posterior lamina of Gerota's fascia medially, creating the boundary of the posterior pararenal space; this fascia must be incised to reach the renal hilum during retroperitoneal dissection.

Fascial Anatomy — Critical for Retroperitoneal Surgery

• An anterior lamina (fascia of Toldt) — thin, fuses with posterior peritoneum.
• A posterior lamina (fascia of Zückerkandl) — thicker, lies between the kidney and posterior abdominal wall.

Practical Surgical Summary

• Campbell-Walsh-Wein Urology (Retroperitoneal anatomy chapter)
• Grainger & Allison's Diagnostic Radiology (Percutaneous renal access — anatomical factors)