it occurs , most often , in patients receiving anticoagulation therapy or in patients with either inherited or acquired clotting disorders11 ) . it has also been reported to occur following trauma , harvesting an anterior iliac crest bone graft and hip arthroplasy4,8,14 ) . it can occur even in a healthy patient who is not undergoing anticoagulant treatment or suffering from a clotting disorder6 ) . it can cause severe pain in the affected groin , hip and thigh , and it can cause quadriceps weakness . other associated findings may include a fall in the hematocrit , tachycardia , hypotension , abdominal pain and a palpable mass , depending on the severity of hemorrhgage11 ) . because of the rareness of this condition , the optimal treatment of iliacus muscle hematoma with associated femoral neuropathy remains controversial . we report here on a rare case of a spontaneous iliacus muscle hematoma that caused femoral neuropathy in a patient who was taking warfarin for occlusive vascular disease with the discussion of the treatment . a 55-year - old male presented with severe pain and numbness in the groin that radiated to the left anterior thigh . after the sudden onset of the pain , weakness on the left lower extremity developed and this had worsened for one week . he had a previous history of a thrombectomy in the left femoral artery two years before and in the left external iliac artery one month before . his prothrombin time international normalized ratio was 1.6 , the hemoglobin was 9.7 g / dl and the platelet count was 22310/l . physical examination revealed paresis of the left quadriceps muscle with strength of 4/5 and a diminished knee jerk reflex . the femoral , popliteal and dorsalis pedis pulses were palpable but slightly weak and no change in the skin color was found . he kept the left knee flexed and complained of aggravated pain when he extended the knee . but computed tomography ( ct ) angiography and doppler ultrasonography revealed patent proximal arteries and intact flows on the lower extremities . 1 ) . because the left psoas muscle was compressed and displaced by the hematoma compared with right psoas muscle and the femoral nerve runs between the psoas tendon and the iliacus muscle , compression or displacement of the left femoral nerve was suspected . the warfarin was immediately discontinued and he was managed with pain control and regular neurological assessment . electromyography and nerve conduction study showed left femoral neuropathy . after confirming the normalization of his coagulation parameters , percutaneous catheter insertion was performed under ultrasonographic guidance for aspiration and drainage of the hematoma . however , only a small amount of the hematoma was drained and then surgical evacuation of the hematoma via the left retroperitoneal approach was performed . soon after making the incision on the iliacus fascia , old blood clot gushed out . the hematoma was gently evacuated with the suction and forceps and irrigated , and a jackson pratt drain was placed for continued drainage . abdominal ct scan showed a decreased amount of the hematoma one month after the surgery ( fig . 2 ) . he demonstrated recovery of his femoral nerve function , with an improvement of the quadriceps strength to grade 4/5 at the 1-year - follow - up examination , but limping in his left leg remained . the femoral nerve develops within the body of the psoas muscle from the posterior division of l2-l4 . the femoral nerve then runs between the psoas tendon and the iliacus muscle beneath the iliacus fascia to the femoral canal , under the inguinal ligament11 ) . anatomic studies have revealed that the fascia overlying the iliacus muscle and the femoral nerve is strong and not easily stretched in the presence of underlying hematoma formation10 ) . as a result , femoral nerve compression occurs along the iliopsoas gutter , where it is also at the most risk for ischemia due to the poor vascular supply to this region of the nerve . in addition , the hematoma may track down the iliacus muscle into the femoral canal and compress the femoral nerve against the rigid inguinal ligament , resulting in further ischemia and resultant neuropathy10,11 ) . goodfellow et al.3 ) demonstrated that a hematoma that is responsible for femoral nerve palsy is necessarily situated in the iliacus muscle and not in the psoas muscle . fluid injected into the iliacus muscle or fascial sheath produces high pressure , and this compresses the femoral nerve against the psoas muscle tendon and induces an ischemic femoral neuropathy . an iliacus muscle hematoma never drains spontaneously , rather , it persists for a long period of time and induces chronic compression of the femoral nerve and then the hematoma becomes organized16 ) . in the present case , the hematoma was found within the iliacus muscle and not in the psoas muscle . it might have stretched the iliacus fascia , and compressed and displaced the femoral nerve . although hematoma of the iliacus muscle has been reported to occur following trauma , harvesting an anterior iliac crest graft , hip arthroplasy , and even in a normal patient , it has been reported primarily in patients suffering from hemophilia and those receiving heparin or oral anticoagulant therapies4,6,8,11,14 ) . the incidence of retroperitoneal hemorrhage has been reported at 1.3 - 6.6% of the patients undergoing therapeutic anticoagulation and at 5.5% and 10.4% of the patients with hemophilia1,2,11 ) . therapeutic anticoagulation is a frequently utilized treatment for a number of conditions , including atrial fibrillation , deep vein thrombosis , pulmonary embolism and so on . as the number of patients undergoing anticoagulation therapy increases the treatment of iliacus muscle hematoma with associated femoral neuropathy remains controversial because of the rareness of this condition . treatment depends on the speed of onset , the volume and the degree of neurological impairment6 ) . a conservative approach is justified for hemodynamically stable patients with smaller hematomas , moderate neurological symptoms and there is no active bleeding6,11,14 ) . in the case of active bleeding advocated that because of its lower morbidity , transarterial embolization should be considered instead of surgery13 ) . for large haematomas with severe motor function inhibition , if the lesion progresses or there is evidence of neurological worsening , then surgical treatment is mandatory by decompression and drainage5,11,16 ) . parmer et al.11 ) suggested when surgical hematoma evacuation was performed at the first identification of neuropathy , a full return of function is more likely to occur , and those patients who are treated conservatively for an extended period despite the presence of femoral neuropathy continue to have prolonged neurological deficit despite eventual intervention . in one series , all the patients who had a femoral motor deficit and who were conservatively treated or underwent surgical drainage after 48 hours had a permanent femoral nerve distribution paresis16 ) . they reasoned that early fasciotomy with or without hematoma evacuation should be considered in order to provide rapid decompression and to minimize the chance of permanent nerve injury . nevertheless , they did not provide any specific information regarding the hematoma volume and management decisions12 ) . in the present case , the patient 's pain and motor weakness became worse despite of initial conservative management , and surgical evacuation of the hematoma was performed two weeks after the onset of pain and weakness . although there was improvement in the quadriceps power after the surgery , he still walked with a limp in his left leg . an alternative to open surgical treatment is percutaneous decompression . merrick et al.7 ) reported the return of nerve function by percutaneous decompression of a retroperitoneal hematoma and they suggested that percutaneous drainage may represent a reasonable alternative to or the first step in surgical treatment . of note , this treatment can be used only for liquid hematomas and it would not be useful for patients whose diagnosis is delayed until they already have organized hematomas14 ) . in the present case , at the time two weeks after the onset of symptoms , the organized hematoma made percutaneous aspiration or drainage impossible , and this led us to perform open surgical treatment . spontaneous iliacus muscle hematoma should be considered in the differential diagnosis of leg pain in a patient who is on anticoagulation therapy . although there is no clear consensus for the treatment of femoral neuropathy associated with iliacus muscle hematoma , the development of associated femoral neuropathy mandates early operative intervention . delays in the surgical evacuation of a hematoma for decompressing the femoral nerve can lead to a prolonged or permanent disability .
spontaneous hematomas of the iliacus muscle are rare lesions and these are seen in individuals receiving anticoagulation therapy or patients with blood dyscrasias such as hemophilia 
 . it can cause femoral neuropathy and resultant pain and paralysis . although there is no clear consensus for the treatment of femoral neuropathy from iliacus muscle hematomas , delays in the surgical evacuation of hematoma for decompression of the femoral nerve can lead to a prolonged or permanent disability . 
 we report here on a rare case of a spontaneous iliacus muscle hematoma that caused femoral neuropathy in a patient who was taking warfarin for occlusive vascular disease and we discuss the treatment .