Abdominal Hematoma

Etiology

Rectus sheath hematomas result from bleeding of the epigastric vessels or their perforator branches in the rectus abdominis muscle sheath[3]. Although rarely life-threatening, they can be severe and lead to hemodynamic instability. However, in most cases, rectus hematoma is self-limiting and usually spontaneously resolves.

Like in other types of bleeding, the cause can be due to the bleeding tendency, anticoagulation, or injury to the vessels. Vascular injury may occur due to external abdominal trauma, trauma during surgery (iatrogenic), or intense contraction of the rectus muscles during activities associated with Valsalva maneuver, as in severe retching, vomiting, or straining [7][8]. In most cases, the hematoma is localized. But in people with excessive loose connective tissue, the hematoma can spread to above the umbilicus, the contralateral side, or become intraabdominal. Risk factors include the use of anticoagulant medications, advanced age, female gender, and intense physical activity. With the increased use of anticoagulation, the rates of rectus sheath hematoma appear to be on the rise.

Epidemiology

Rectus sheath hematomas are uncommon [9][10]. The exact incidence of rectus sheath hematoma is not known as the condition is often misdiagnosed or undiagnosed. Some studies report an incidence of 1.5% to 2% in hospitalized patients.

Overall, rectus sheath hematoma is more common in females than males. A higher female incidence has been linked to decreased muscle mass. While pregnancy is a risk factor in women, trauma and exercise seem to be the most common causes in men. Rectus sheath hematomas are more common on the right side, and the majority are located in the lower quadrant of the abdomen below the arcuate line. 

Pathophysiology

Rectus sheath hematoma is caused by rupture of an epigastric artery or one of its perforating branches. The vessel injury may be due to blunt or penetrating trauma, surgery, or strong contractions of the rectus muscle. Since the epigastric arteries run deep along the posterior rectus sheath, making a diagnosis during a physical exam is difficult, especially in patients who have obesity. The hematoma is usually posterior to the rectus muscle fibers, subcutaneous fat, and skin. Palpating a tender firm bulge is the most common physic exam finding. The fluctuation sign of a fluid collection is not usually possible to detect due to the deep location of the hematoma. The lower quadrants of the abdomen are usually involved because of the long epigastric branches and the lack of a tamponade effect from the loose connective tissues of the rectus sheath.

History and Physical

The typical presentation of a rectus sheath hematoma is abdominal pain and its associated symptoms like nausea and vomiting. The pain is often sudden in onset, sharp, and does not radiate. In extremely rare cases, the hematoma may be large and present with hypovolemia, tachycardia, and tachypnea. Physical exam usually reveals a palpable localized mass that is non-pulsatile. The Fothergill sign is a mass in the abdominal wall that does not cross the midline and does not change with flexion of the rectus muscles. This suggests a rectus sheath hematoma and is useful to determine if the abdominal mass is within the abdominal wall or intraabdominal cavity. It is not a highly sensitive sign and is often inconclusive in individuals who are obese.

The clinician should obtain a thorough medical history to determine the presence of any risk factors like surgery, coughing, constipation, asthma, bronchitis, anticoagulation therapy, and use of oral anticoagulants and corticosteroids.

Evaluation

Ultrasound is the first test of choice to confirm a rectus sheath hematoma diagnosis after basic blood work, and coagulation profile are obtained. The hematoma appears as hypoechoic space in the posterior rectus sheath. Further information like the size and exact location of the hematoma can be obtained from the ultrasound study. If the ultrasound study is inconclusive, a CT scan is the next test. It can show more details about the location, size, and extension of the hematoma. When intravenous contrast is administered with the CT scan, active bleeding can be detected by the presence of the contrast in the form of blush in the hematoma if the bleeding is active.

Unless a contrast is visualized in the hematoma, the differential diagnosis of a fluid collection in the rectus sheath should not be ignored. If the diagnosis of hematoma is still in doubt after imaging, needle aspiration can be performed to differentiate a hematoma from an abscess. However, with needle aspiration, there is a risk of puncture the bladder, bowel, or a hernia.[11]

Evaluation of the hematoma should be part of the comprehensive evaluation of the patient's condition. General assessment addressing the related factors and conditions causing the hematoma or as a complication of the hematoma is necessary for a proper evaluation[12]. Simultaneous treatment of the underlying condition and the possible or pending complications is mandatory for successful management. 

Treatment / Management

Treatment of rectus hematomas depends on the severity of symptoms, size, the stability of the hematoma, and the underlying pathology. The goal of the treatment is to relieve or minimize symptoms, prevent complications, and address the underlying condition. Proper patient's condition assessment, volume replacement, and correction of any coagulation abnormalities are important initial measures that should be performed before considering more aggressive steps.

If the hematoma is enlarging and or causing significant blood loss, intervention should be taken to stop the bleeding. Interventional radiology localizing and embolizing the bleeding vessel is the appropriate first modality of treatment to use. In most cases, this is successful and sufficient to stop the bleeding, especially with the confined space and the pressure created that counteracts the flow of bleeding.

In a few cases of ongoing bleeding that is not amenable to radiologic intervention or if the service is not available, surgical control of the bleeding and evacuation of the hematoma is necessary. Controlling the bleeding is achieved by ligating the bleeding vessel (epigastric vessel) surgically.

In most cases, bleeding stops after enough pressure build-up inside the rectus sheath. The size of the developed hematoma varies according to the size and pressure of the bleeding vessel, expandability of the rectus space, and the presence and severity of coagulation abnormalities. Once the bleeding stops and the hematoma size stabilizes, treatment is usually directed on the relief of the symptoms. There is no urgency in evacuating the hematoma. In fact, maintaining the pressure inside the hematoma at the initial phase is important to prevent rebleeding. Large hematomas can be drained percutaneously after stabilization and recovery from the acute phase. Small hematomas can be left to be reabsorbed spontaneously to avoid unnecessary intervention.  

Patients with rectus sheath hematoma can be treated as outpatients as long as the hemodynamic status is stable and there is no change in the hematocrit. Patients on anticoagulation therapy should be admitted to ensure that the hematoma is not expanding.[7][13](B3)

Differential Diagnosis

Conditions presenting with a mass:

• Abdominal wall tumors (benign and malignant)
• Abdominal wall abscess
• Abdominal wall hernia[14]

Conditions presenting pain or acute abdomen:

• Peptic ulcer disease
• Bowel perforation
• Tubo-ovarian abscess
• Appendicitis
• Cholecystitis
• Diverticulitis[15]
• Urinary tract infection
• Pancreatitis.

A comprehensive history, physical exam, and a low index of suspicion will usually identify the pathology, confirm the diagnosis and assist in the management planning.

Prognosis

Most cases of rectus hematomas are self-limited, non-life-threatening, and can be identified and treated successfully with minimal interventions. Even though fatalities have been reported, most of the fatalities have come to light during an autopsy. Rectus sheath hematoma mortality is higher in elderly individuals who are on oral anticoagulants. Pregnant women are at a higher risk for mortality. Anecdotal old reports reveal a mortality rate of 15% in the mother and nearly 50% in the fetus. However, it is important to know that these data were collected before the wide use of ultrasound and CT scans. Today, these imaging modalities can rapidly diagnose the condition.

Complications

The main consequence of undiagnosed or untreated rectus hematomas is pain. In addition to pain, severe bleeding is serious and can be life-threatening. Therefore severe bleeding should be promptly identified and aggressively treated. Another potential complication is abscess formation. As in any blood collection that is not drained, there is always a chance of superseding infection and the development of an abscess. Draining of abscess becomes mandatory when it develops.