sciatic hernias are one of the rarest types of hernia and often pose diagnostic difficulty to clinicians . imaging is often required to confirm the diagnosis and usually involves computed tomography ( ct ) or magnetic resonance imaging ( mri ) . to our knowledge , we report the 115th case of sciatic hernia in the literature who had a falsely negative ct but had the diagnosis confirmed using ultrasonography . an 80-year - old lady was referred to the on - call surgical team by her gp with a 3-week history of a right - sided swelling of the buttock . she had a past medical history of hypertension , osteoarthritis and pemphigus vulgaris and a past surgical history of a perianal abscess requiring incision and drainage . she was allergic to penicillin and took regular oral betamethasone , xylometazoline nasal spray and topical aqueous cream . she did not consume alcohol , was a non - smoker and lived in warden - controlled accommodation . on examination , her cardiac , respiratory and abdominal examinations were normal . digital rectal examination revealed a non - tender stool - filled rectum with no palpable masses . on standing , a swelling on the medial aspect of the right buttock became apparent which was easily reducible , had audible bowel sounds and a positive cough impulse . she was reviewed by the on - call consultant who discharged her with a working diagnosis of possible obturator hernia , with a plan for an outpatient ct of her pelvis and follow - up in clinic . ct scan of the pelvis did not identify a cause for the swelling ( fig .  1 ) . due to the positional nature of the swelling , a gluteal ultrasound was organized , which revealed a large colonic sciatic hernia ( fig .  2 ) . as the patient had minimal symptoms and was not keen for surgical intervention , a plan for conservative management was agreed and the patient was discharged from clinic . figure  1:ct of the patient 's pelvis demonstrating a normal right sciatic foramen ( arrowed ) . us hip rt : confirms reducible herniation of colon in the right sciatic region into the buttock. ) ct of the patient 's pelvis demonstrating a normal right sciatic foramen ( arrowed ) . hip rt : confirms reducible herniation of colon in the right sciatic region into the buttock. ) sciatic hernias are one of the rarest types of hernia and often pose diagnostic difficulty to the clinician . a sciatic hernia is defined as herniation of intraperitoneal contents through either the greater or lesser sciatic foraminae ( fig . the majority of sciatic hernias are found in women ( 77% ) with more than one - third of these being aged 60 or over . the contents are variable and hernias containing ovaries , ureters , bladder , small and large intestine , omentum and dermoid cysts have been reported [ 16 ] . half of patients report non - specific abdominal or pelvic pain and one third have a mass on clinical examination . sciatica , intestinal obstruction , urinary sepsis and hydronephrosis have also been described [ 15 ] . diagnostic laparoscopy or laparotomy is often required to fully evaluate the sac contents and to repair the defect [ 2 , 3 , 5 ] . in symptomatic patients , surgical repair is indicated due to the high risk of bowel strangulation [ 1 , 3 ] . figure  3:pelvis demonstrating the greater ( red ) and lesser ( green ) sciatic foraminae . diagnosis by clinical examination alone is possible in only the minority of cases and imaging is frequently used to confirm the suspicion of sciatic hernia . commonly used imaging modalities are computerized tomography ( ct ) [ 25 ] and mri [ 3 , 4 ] , particularly if the sciatic nerve is thought to be involved . currently , the most commonly used imaging modality of choice is a ct scan with the patient supine . however , if the hernia is only apparent in a dependent position , this can produce a false - negative result , as in our case . the benefit of ultrasound is that it allows for real - time positional assessment of the region of interest , to reduce the risk of missing this rare but significant hernia . due to their rarity , sciatic hernias are often not considered in the differential diagnosis . the authors recommend that all patients presenting with non - specific abdominal or pelvic pain associated with a gluteal swelling should have sciatic hernia considered amongst their differential diagnosis . for patients in which there is a high degree of clinical suspicion for a sciatic hernia and a negative ct , the use of ultrasonography for positional defects may be a useful aid to confirming the suspected diagnosis .
sciatic hernias are one of the rarest types of hernia and often pose diagnostic difficulty to clinicians . we report a case of an 80-year - old lady with a sciatic hernia who had a falsely negative computed tomography ( ct ) but was found to have a colonic hernia on ultrasonography . 
 the authors recommend that for patients in which there is a high degree of clinical suspicion for a sciatic hernia and a negative ct , ultrasonography may be considered as a useful imaging modality to confirm the diagnosis .