INTRODUCTIONThe Tailgut cyst (cystic hamartoma) is an uncommon congenital disease of presacral retrorectal space and is embryologically part of some forms of enteric cysts. It is a benign malformation, although cases have been described in neoplastic degeneration.PRESENTATION OF CASEA caucasian 24 year old female presented shortly after childbirth with hypogastric abdominal discomfort associated with rectal tenderness, bleeding and moderate urinary symptoms for about three weeks. No previous similar episodes were reported. The patient was not suffering from haemorrhoids or inflammatory disease of the gastrointestinal tract.Clinical examination revealed no significant abnormalities or in the perianal area and gluteal surface.Digital rectal examination was suspicious of the presence of a presacral retrorectal mass. However, it could not exclude a trans-sphinteric perianal fistula. There was no fistulous communication with the exterior and the pain seemed to be more pronounced in the rectum.MRI, which has a diagnostic accuracy of 76–100% for the detection of any perianal fistulae, was performed and demonstrated the presence of a retrorectal cystic hamartoma (Tailgut cyst).DISCUSSIONThe most common retrorectal space cystic lesions includes epidermoid cysts, dermoid cysts and enteric cysts. It presents with pelvic pain, and sometimes with local abscess, secondary to a sinus cyst. There can also be a communication between Tailgut cyst and fistula; in the absence of primary infection may develop postinflammatory fibrosis. Radiological investigation is carried out by TRUS, CT and MRI. During MRI, on T1-weighted images, the signal intensity may change from hypointense to hyperintense as protein concentration increases, as well as in the case of bleeding. On T2-weighted images, signal intensity of mucinous fluids can decrease from highly hyperintense to hypointense with increasing protein concentration and viscosity.CONCLUSIONMRI is a non-invasive useful imaging investigation with high diagnostic accuracy when a retrorectal cyst is suspected. Despite its rarity, Tailgut cyst should be considered, both for acute complications, like infection or bleeding, and for the risk, however infrequent, of neoplastic degeneration.

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SummaryA lung cyst is defined as a round parenchymal lucency or area of low attenuation with a thin wall. Although lymphangioleiomyomatosis (LAM) and Langerhans cell histiocytosis (LCH) are the most frequently encountered causes, the differential diagnosis for diseases characterised by diffuse lung cysts is broad ranging from isolated chest disorders to rare multisystem diseases. This article will illustrate and describe the spectrum of diseases associated with air cysts at high-resolution CT (HRCT), highlighting disorders in which the HRCT findings can be diagnostic.