A rare, deceptive cause of lower abdominal pain: ilio-femoral septic thrombophlebitis

Clinical History

Young, G0P0 non-pregnant obese female seeking attention at Emergency Department because of fever (maximum 39°C) and worsening left-sided lower abdominal pain since 48 hours. Physically, left-sided pelvic tenderness withour peritonism. No urinary or genital complaints.
Laboratory tests consistent with severe inflammatory state including leukocytosis (17.000 cells/mmc) and elevated C-reactive protein (326 mg/L).

Imaging Findings

Requested to rule out acute diverticulitis and adnexal emergencies, initial CT (Fig.1) showed a left-sided subperitoneal abscess surrounded by inflammatory fat stranding, exerting mass effect on the hyperaemic adjacent fascia and the urinary bladder. Changes were located along the ilio-femoral vessels: the luminal non-opacification with enhancing walls of the vein and perivascular inflammation were attributed to infectious thrombosis. Without diverticula and pericolonic abscesses, the oedematous submucosal thickening of the sigmoid colon was interpreted as reactive. Further questioning disclosed ipsilateral knee trauma two months earlier, with local suppuration treated topically.
Transvaginal ultrasound (Fig.2) confirmed normal-appearing uterus and adnexa. Colour Doppler sonography (not shown) confirmed near-complete thrombosis of external iliac and proximal common femoral vein, which was treated with intravenous antibiotics plus fundaparinux.
MRI (Fig.3) confirmed mass-forming subperitoneal perivascular phlegmon, abscess cavity with peripheral enhancement and strong diffusion restriction.
After clinical and laboratory improvement, repeated MRI (Fig.4) showed disappeared abscess and decreased perivascular phlegmon.

Discussion

Ilio-femoral septic thrombophlebitis (IFST) represents a rare occurrence, which is mostly reported following abortion, delivery, gynaecological diseases or surgery, and may develop after repeated non-sterile self-injection of recreational drugs at the groin [1-4]. Alternatively, IFST may occasionally complicate post-traumatic conditions or infections in the lower extremities [5-7].
The unspecific clinical manifestations of IFST include pelvic or flank pain, fever, leg oedema, leukocytosis and abnormal inflammatory markers. Unfortunately, if unrecognised, IFST may be further complicated by septic embolisation, multiorgan failure, respiratory and haemodynamic compromise. Therefore, in the appropriate clinical context, this condition should be considered among possible causes of pelvic complaints with persistent or spiking fever despite broad-spectrum antibiotic therapy [1, 4].
Prompt investigation with colour Doppler ultrasound (CDUS) may readily detect most cases of venous thrombosis as distended, non-compressible veins with absent flow. However, contrast-enhanced multidetector CT increasingly represents the initial investigation in patients with abdomino-pelvic symptoms or suspected deep infection: CT consistently and panoramically shows the extent of deep thrombophlebitis without anatomic limitations of CDUS. At CT, the involved veins appear more or less enlarged with partially or entirely non-opacified lumen. Additionally, similarly to Lemierre’s disease in the neck, CT shows signs consistent with superinfection such as thickened and prominently enhancing venous wall, inflammatory hyperattenuation of the perivascular fat planes, occasionally intraluminal gas bubbles. As in the hereby presented patient, perivascular inflammation may occasionally become frankly tumefactive or form abscess collections, thus resulting in challenging CT differential diagnosis from bowel-related or gynaecologic acute infections. Owing to the intrinsically high soft tissue contrast, MRI optimally depicts perivascular oedema, phlegmon and abscesses without ionising radiation exposure [1-3]. Furthermore, CT imaging allows detecting or excluding signs of haematogenous dissemination, particularly in the lungs, brain and musculoskeletal system [2, 3].
As in this case, correct imaging diagnosis allows timely treatment: a combination of antibiotics and anticoagulation with low-molecular-weight heparin effectively cures most cases of IFST [1, 4, 8].

Differential Diagnosis List

Final Diagnosis

Iliofemoral venous septic thrombophlebitis with abscess

URL:	https://www.eurorad.org/case/14925
DOI:	10.1594/EURORAD/CASE.14925
ISSN:	1563-4086