Rectus sheath hematoma with low molecular weight heparin administration: a case series

For greater than a decade, prophylactic administration of low molecular weight heparin (LMWH) has risen for hospitalized patients and is an encouraged practice of deep vein thrombosis (DVT) prophylaxis. Therapeutic dosing is considered the standard medical care for many common diagnoses such as pulmonary embolism, acute DVT, acute coronary syndrome, and atrial fibrillation [1]. Well established adverse outcomes from LMWH include gastrointestinal bleeding, intracranial hemorrhage, thrombocytopenia, and retroperitoneal bleeding [2]. Rectus sheath hematoma (RSH) is considered an uncommon bleeding complication that can occur spontaneously, after trauma, or as a result of anticoagulation therapy. Cases of RSH associated with subcutaneous LMWH injection have been reported [3–7]. We present a case series of three patients with RSH associated with subcutaneous enoxaparin injection. These were confirmed by computed tomography (CT) at our facility during a three month period. We propose that RSH may be an underreported, significant cause of morbidity and perhaps mortality in the setting of LMWH use. Diagnostic and therapeutic interventions as well as preventive strategies we have implemented at our institution are discussed.

Rectus sheath hematoma occurs due to bleeding in the rectus sheath. This bleeding occurs either from a tear of the rectus muscle or from damage to its blood supply, including the superior and inferior epigastric arteries and branches. The rectus abdominis muscle and the epigastric arteries are surrounded by an aponeurotic sheath above the arcuate line. Below the arcuate line the posterior sheath compromises only the transversalis fascia and thus, bleeding from the inferior epigastric artery in this area can be more severe. The superior and inferior epigastric arteries anastomose around the umbilicus creating a higher concentration of vessels in this area [8, 9]. There is some evidence to suggest that aging and deconditioning of the abdominal muscles results in protuberant tissue with increased vascularity which may predispose the elderly to vessel injury and bleeding [4, 5].

Causes of RSH can include trauma, surgery, vigorous muscle contractions from coughing or straining, intraabdominal injections, and pregnancy. RSH can also occur spontaneously. Risk factors include anticoagulation therapy, cough, older age, thin body habitus, central obesity, pregnancy, female gender, recent abdominal surgery, external trauma, medical conditions causing coagulopathy, persons receiving multiple types of abdominal subcutaneous injections, and renal insufficiency [3–5, 7, 8].

The incidence of RSH is suspected to be on the rise; however, this is difficult to determine. In 1999, Klingler et al. found an incidence of 1.8% among 1257 hospitalized patients being evaluated by ultrasound for abdominal pain [10]. Cherry et al.’s case review at the Mayo Clinic found 126 patients over a 10 year period and illustrates the difficulty in determining an actual incidence rate [3]. Enoxaparin drug information provided by Lexi-Comp, Inc. reports that major hemorrhage occurs less than 1 to 4% and includes intracranial, retroperitoneal or intraocular hemorrhage. It also reports injection site hematoma as a local adverse reaction occurring at a rate of 9%. It is unclear whether RSH is grouped into the major hemorrhage or local injection site category. Lack of a ICD-9 code and lumping the diagnosis into “major bleeding” categories in large trials such as TIMI and GUSTO makes identifying the true incidence difficult [5].

Symptoms of RSH include abdominal pain, nausea, and vomiting. The symptoms can mimic conditions such as diverticulitis, appendicitis, cholecystitis, incarcerated inguinal hernia, ovarian cyst torsion, or acute pancreatitis. Physical exam often reveals a painful, firm abdominal mass corresponding to the rectus sheath. Ecchymosis does not tend to appear until 2–5 days following the hematoma [3, 4, 7, 11]. When unrecognized, RSH has resulted in inappropriate invasive procedures such as open laparotomy; however, criteria have been proposed to prevent this. Maharaj et al. recommended using physical exam maneuvers to differentiate intraabdominal from abdominal wall pathology. One such maneuver, described by Carnett in 1962, involves palpation of the tender abdomen in the supine and half-sitting positions, respectively. With this maneuver, intraabdominal processes will be most tender supine and will be protected by the contracted rectus muscle when the patient is sitting. Abdominal wall processes will remain tender in both positions [12].

Two main imaging modalities for diagnosis of RSH are ultrasound and CT. Ultrasound is not as sensitive as CT; however, it is typically more rapid and does not expose the patient to radiation. CT is useful because it is 100% sensitive and specific and can determine the presence of active bleeding [10, 13]. In order to better classify radiologic findings and suggest appropriate management strategies for findings documented, Berna et al. has described a classification system of RSH based on CT results. This classification system is divided into three types of RSH. Type I TSH represents an intramuscular, unilateral hematoma not dissecting into a fascial plane. Type II RSH represents an intramuscular, unilateral or bilateral hematoma which does not dissect into the fascial plane, but without occupation of the prevesical space. Type III RSH may or may not involve muscle, and blood can be seen within the transversalis fascia, peritoneum, and prevesical space [14].

Treatment of Type I and Type II RSH is usually conservative. Treatment of Type III RSH frequently involves blood transfusion [14]. Invasive treatment includes angiography with embolization or surgical management with exploration, hematoma evacuation, and ligation of bleeding vessels; however, this is only indicated if the RSH is progressive or if the patient is hemodynamically unstable despite adequate resuscitation [13]. Morbidity related to RSH includes all required interventions mentioned here as well as prolonged hospital stay and increased healthcare costs. Mortality data is difficult to determine given the lack of data tracking [3, 7, 15].

The association between RSH and LMWH is not well understood. The SYNERGY trial has demonstrated an increased bleeding risk when switching from one type of heparin product to another (i.e. from unfractionated heparin to LMWH), but this was not a contributing factor in our cases [15]. Injection technique has been implicated in numerous case reports [3–7]. The Lovenox® (Sanofi-aventis U.S., Bridgewater, NJ) package insert advises that the injection sites should alternate between the left and right anterolateral and left and right postero-lateral abdominal wall, avoiding the umbilicus by at least two inches. There is a warning not to inject intramuscularly. Instructions also state that the whole length of the needle should be introduced into a skin fold and advise that the skin fold should be held throughout the injection interval. Consideration of alternate injection sites such as the posterior deltoid has been suggested for higher risk patients [5, 12].

The facts of these cases were reviewed for quality improvement and were presented at a morbidity and mortality conference at our facility. This led to a systems review and re-education of nursing staff, including injection technique, site selection, and identification of higher risk patients. In addition, the eGFR is now calculated and reported with basic lab work, allowing for ease of renal dose adjustments.

A series of cases at our institution highlight RSH as a serious potential complication of subcutaneous LMWH administration. Complicated coding schematics, with no existing ICD-9 code for the purpose of documentation and tracking of such events, may attribute to underreporting of RSH in both the inpatient and outpatient setting. Diagnosis of RSH can be accomplished with ultrasound or CT and management of RSH is usually conservative.

We encourage other practitioners and institutions to be aware of RSH and support the emphasis on staff and caregiver training as an important factor in its prevention. Recognition of higher risk patients, careful injection site selection, and proper injection technique should be included in this training.

For case number one, written, informed consent was obtained from the patient’s next of kin for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-In-Chief of this journal.

For case numbers two and three, written, informed consent was obtained from the patients for publication of these case reports and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.