Sciatic Hernia

Sciatic hernia is protrusion of peritoneal or retroperitoneal contents through the greater or lesser sciatic foramen into the gluteal region. It is the rarest of the pelvic floor hernias, with only a few hundred cases described. It affects adults over 40 years of age, women slightly more than men, and is sometimes bilateral.

Anatomic types of the greater foramen: suprapiriform (the commonest, about 60%), infrapiriform and, uncommonly, the lesser foramen below the ischial spine. The sciatic nerve and the gluteal vessels lie in the foramen in close relation to the neck of the sac.

Causes

• Weakness of the pelvic floor with age and weight loss
• Multiparity
• Chronic raised intra-abdominal pressure
• Pelvic surgery, trauma and tumor in the pelvis
• Congenital defects in children

Contents may include small bowel, ovary, fallopian tube, ureter, bladder, colon or omentum. Complications: bowel obstruction, strangulation, ureteric obstruction with hydronephrosis, and sciatic nerve compression.

• A soft, reducible gluteal mass in the posterior buttock, often noticed on straining, with a cough impulse
• Sciatica or gluteal pain from nerve compression, worse on sitting or on prolonged standing
• Intestinal obstruction with colicky pain and vomiting when bowel is trapped
• Urinary symptoms and flank pain when the ureter is involved
• Red flags: a tender irreducible gluteal mass, signs of obstruction, ischemia, urinary retention or hydronephrosis

1. CT of the abdomen and pelvis with intravenous contrast is the investigation of choice: a defect in the posterior pelvic wall, the sac and its contents, and the relation to the piriformis, the sciatic nerve and the gluteal vessels.
2. MRI for soft tissue detail and the nerve.
3. Ultrasound of the buttock to show a mass with bowel peristalsis.
4. Intravenous urography or CT urography when the ureter is suspected.
5. Laboratory tests: full blood count, C-reactive protein, urea and electrolytes, and lactate in acute presentations.

Differentials: gluteal abscess, lipoma, sarcoma, hematoma, inferior gluteal artery aneurysm, perineal hernia, sciatica from spinal disease, piriformis syndrome.

1. Acute presentation with obstruction or strangulation: nil by mouth, nasogastric decompression, IV crystalloid 20 mL/kg initially, cefazolin 2 g IV with metronidazole 500 mg IV, and emergency surgery.
2. Operative approaches:
   • Transabdominal (laparoscopic or open): reduce the contents, check bowel viability, resect non-viable bowel, free the sac and close or obliterate the foramen. Fix a mesh or use direct suture to the sacrospinous ligament and piriformis, taking care to avoid the sciatic nerve and the superior and inferior gluteal vessels.
   • Transgluteal approach: for small hernias with a palpable sac, with incision through the gluteus maximus fibers.
   • Combined approach in complex cases.
3. Mesh choice: polypropylene in clean cases, and biological mesh in contaminated cases.
4. Perioperative care: cefazolin 2 g IV before incision (3 g if over 120 kg), enoxaparin 40 mg SC once daily for 7 days, paracetamol 1 g orally every 6 hours, and treatment of constipation.
5. Complications: recurrence (rare), nerve injury, gluteal hematoma, infection and ureteric injury.
6. Children: cefazolin 30 mg/kg IV (maximum 2 g), and paracetamol 15 mg/kg orally every 6 hours.

Follow-up at 2 weeks, 3 months and 12 months. Counsel on avoiding heavy lifting for 6 weeks and on reporting any new buttock lump.