Abdominal Wall Hematoma

An abdominal wall hematoma is a collection of blood in the subcutaneous fat or in the muscle and fascial planes of the anterior and lateral abdominal wall, outside the peritoneal cavity.

It arises from injury to the superficial or deep epigastric vessels, the circumflex iliac vessels or small muscular perforators.

Causes

• Blunt trauma (seat belt, handlebar, kick) and penetrating injury

• Laparotomy and port wounds, paracentesis and drain insertion

• Subcutaneous injections of enoxaparin, heparin or insulin

• Anticoagulants, antiplatelet drugs, thrombocytopenia, hemophilia and acquired factor deficiency

• Violent coughing or vomiting

Wound hematoma complicates 1 to 5% of abdominal operations, and risk rises with obesity, anticoagulation and hypertension.

Most small collections resorb over 2 to 6 weeks. The wall can hold 1 to 2 L before the patient looks unwell.

Complications

• Expanding hematoma with hypovolemia

• Infection and abscess

• Skin necrosis and wound dehiscence

• Chronic seroma

• Abdominal compartment syndrome in massive bleeds

A seat belt sign (a linear bruise across the lower abdomen) marks deeper injury, with hollow viscus or mesenteric injury in roughly 20 to 30%, and a lumbar flexion-distraction fracture in some.

• Localized swelling and ecchymosis, pain that is worse on moving, coughing or tensing the abdominal muscles

• A firm, tender mass that is fixed to the wall, with bruising that tracks into the flank or groin

• Pain on lifting the head from the pillow (the abdominal wall muscles are tense), which separates a wall lesion from an intraperitoneal one

• Tachycardia, hypotension and falling hemoglobin in large bleeds

• Clinical assessment with vital signs, and the abdominal wall tenderness test (pain persists or worsens when the muscles are tensed).

• Hemoglobin, platelet count, INR, aPTT, creatinine, and anti-Xa level or drug-specific assays in anticoagulated patients. Group and screen.

• Ultrasound: the first test for stable patients, showing a heterogeneous collection, its layer and size.

• CT with intravenous contrast: defines extent, active extravasation (a contrast blush), hematocrit levels, and associated intra-abdominal injury. It is mandatory after significant blunt trauma with a seat belt sign.

• Repeat hemoglobin every 6 hours for the first 24 hours in significant bleeds.

Small stable hematoma: rest, cold compress for 24 to 48 hours, then warm compress, and an abdominal binder for comfort. Paracetamol 1 g orally every 6 hours (maximum 4 g a day). Avoid NSAIDs while bleeding. Children: paracetamol 15 mg/kg orally every 6 hours.

Anticoagulant-related bleeding

• Hold the anticoagulant, and reverse when the bleed is large or the patient is unstable.
• Warfarin: phytomenadione 5 to 10 mg IV by slow infusion and four-factor prothrombin complex concentrate 25 to 50 units/kg IV once (dose by INR).
• Unfractionated heparin: protamine 1 mg for each 100 units given in the previous 2 to 3 hours (maximum 50 mg), IV slowly.
• Enoxaparin: protamine 1 mg for each 1 mg enoxaparin given in the last 8 hours (0.5 mg for each 1 mg between 8 and 12 hours).
• Dabigatran: idarucizumab 5 g IV (two 2.5 g doses).
• Apixaban and rivaroxaban: prothrombin complex concentrate 50 units/kg IV once.
• Tranexamic acid 1 g IV over 10 minutes, then 1 g IV over 8 hours (reduce in renal impairment).

Resuscitation: crystalloid, then red cells when hemoglobin falls under 70 g/L (under 80 g/L with cardiac disease), and platelets when under 50 × 10^9/L.

Active bleeding: superselective angioembolization of the epigastric or circumflex vessels (success about 90%) in stable patients. Surgical evacuation with ligation of the bleeding vessel when embolization is unavailable or fails, or when compartment syndrome, infection or skin compromise develops.

Infected hematoma: drainage, cefazolin 2 g IV every 8 hours with metronidazole 500 mg IV every 8 hours until culture results, then oral therapy to complete 7 days.

Post-surgical wound hematoma: evacuate if tense, expanding or painful, with irrigation and hemostasis.

Restart anticoagulation once bleeding is controlled (usually 48 to 72 hours, earlier for mechanical valves). Follow-up with ultrasound at 2 to 4 weeks for large collections. Counsel on rotating injection sites and avoiding heavy lifting for 4 to 6 weeks.