A 51-year-old female was admitted to the emergency department of our hospital with sudden onset of general abdominal and back pain with nausea. Past medical history included no special feature. Laboratory tests revealed no important findings. Abdominal computed tomography (CT) scan and magnetic resonance imaging (MRI) were performed after ultrasonography (US) examination.
Contrast-enhanced abdominal CT images at axial (Fig. 1a, b, c) and sagittal (Fig. 1d) planes demonstrate stranding of fatty tissues with fluid accumulation in the retroperitoneum. Axial T2-weighted images (Fig. 2a, b) reveal fluid spread between fascial planes with high signal intensity. Axial gadolinium-enhanced fat-suppressed T1-weighted image (Fig. 2c) demonstrates stranding of fascial planes in the retroperitoneum with mild contrast enhancement.
Retroperitoneal fasciitis is characterised by inflammation of retroperitoneal deep soft tissues and fascial fat planes in the abdomen and pelvis caused by the spread of infection from primary sources such as appendicitis, diverticulitis, pyelonephritis, etc. . Fasciitis may originate primarily from retroperitoneum or track into the retroperitoneum following direct or indirect pathways. Some of the cases may not have a definitive source of infection . The spread of inflammation in retroperitoneal fasciitis follows potential spaces and fascial planes along with the retroperitoneal space which is located superficial to the parietal peritoneum and deep to the transversalis fascia .
There is no adequate information about the presenting symptoms of the retroperitoneal fasciitis. Clinical symptoms may differ due to presence of necrotising inflammation in the retroperitoneum. Patients usually present with inordinate abdominal pain. Nerve involvement, muscle oedema and swelling resulting in compartment syndrome may cause severe abdominal pain. Imaging is usually required to find the cause of the symptoms.
First line of imaging that should be preferred in patients suspected with retroperitoneal fasciitis is CT . US has a limited value in the diagnosis since only fluid collections may be depicted by this imaging technique. Retroperitoneal fasciitis presents on CT as asymmetric fascial thickening and enhancement, muscular oedema, fat stranding, gas tracking along fascial planes in the retroperitoneum, nonfocal fluid collections along the fascial planes and abscess formation. Necrotising retroperitoneal fasciitis manifests with transgression of fascial planes, more aggressive rapid clinical course, evidence of vascular thrombosis, haemorrhage and multifocal abscess formation . Inflammatory process is limited to retroperitoneum and bounded by fascial planes that separate retroperitoneum and peritoneal cavity. Presence of gas formation does not always indicate occurrence of necrotising fasciitis. MR imaging may be more helpful in revealing inflammation of fascial and fat planes thanks to greater soft tissue contrast than CT. Inflammation of retroperitoneal fascial planes appears as increased signal intensity on T2-weighted images and enhanced linear fascial planes after gadolinium administration .
Non-necrotising form of necrotising fasciitis can be treated with conservative supportive therapies and antibiotics while surgical debridement with antibiotics therapy is required for necrotising retroperitoneal fasciitis.
In conclusion, retroperitoneal fasciitis may present with nonspecific symptoms however life-threatening complications may occur whether early diagnosis and treatment can not be performed. Imaging plays a crucial role in management of patients with retroperitoneal fasciitis.
 Chingkoe CM, Jahed A, Loreto MP, Sarrazin J, McGregor CT, Blaichman JI, Glanc P (2015) Retroperitoneal Fasciitis: Spectrum of CT Findings in the Abdomen and Pelvis. Radiographics, 35(4):1095-1107. (PMID: 26172354)
 Sugimoto M, Matsuura K, Takayama H, Kayo M, Ie T (2010) Extended retroperitoneal necrotizing fasciitis with genital involvement, resembling fournier gangrene. Surg Infect (Larchmt), 11(5):463-467. (PMID: 20583955)
 Unal E, Onur MR, Akpinar E, Karcaaltincaba M (2017) Primary retroperitoneal fasciitis; A rare cause of acute abdominal pain. Am J Emerg Med, 35(7):1040 e1041-1040 e1044. (PMID: 28274713)
 Lancerotto L, Tocco I, Salmaso R, Vindigni V, Bassetto F (2012) Necrotizing fasciitis: classification, diagnosis, and management. J Trauma Acute Care Surg, 72(3):560-566. (PMID: 22491537)