Imaging Pearls ❯ GU ❯ Urachus
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- “ The urachus is a ductal remnant that arises embryologically, originating from the involution of the allantois and cloaca and extending between the bladder dome and the umbilicus. During normal gestational development, the urachus involutes and its lumen is obliterated, becoming the median umbilical ligament.”
Imaging of the Urachus: Anomalies, Complications, and Mimics ParadaVillavicencio C et al. RadioGraphics 2016; 36:2049–2063 - “The reported incidence of urachal anomalies is approximately one in 5000 population for adults, with a significantly lower rate of one in 150 000 population among infants.There is a higher prevalence in men than women. Most anomalies of the urachus are unexpected, being detected incidentally and more frequently with the increased use of cross-sectional imaging.”
Imaging of the Urachus: Anomalies, Complications, and Mimics ParadaVillavicencio C et al. RadioGraphics 2016; 36:2049–2063 - “Four types of urachal anomalies have been described, on the basis of the location of the abnormal residual patency along the urachal tract: patent urachus (sometimes referred to as urachal fistula), urachal cyst, umbilical-urachal sinus, and vesicourachal diverticulum.”
Imaging of the Urachus: Anomalies, Complications, and Mimics ParadaVillavicencio C et al. RadioGraphics 2016; 36:2049–2063 - “The reported incidence of urachal anomalies is approximately one in 5000 population for adults, with a significantly lower rate of one in 150 000 population among infants.There is a higher prevalence in men than women. Most anomalies of the urachus are unexpected, being detected incidentally and more frequently with the increased use of cross-sectional imaging.”
Imaging of the Urachus: Anomalies, Complications, and Mimics ParadaVillavicencio C et al. RadioGraphics 2016; 36:2049–2063 - “The urachus extends from the anterosuperior surface of the bladder to the umbilicus and lies in the extraperitoneal space of Retzius (or retropubic space) between the transverse fascia and parietal peritoneum. It is accompanied on both sides by the medial umbilical ligaments, which are the obliterated remnants of the umbilical arteries and may on occasion merge with the urachus, causing it to mildly deviate from the midline. The length of the urachus ranges from 3 to 10 cm and it generally has an approximate diameter of 8–10 mm.”
Imaging of the Urachus: Anomalies, Complications, and Mimics ParadaVillavicencio C et al. RadioGraphics 2016; 36:2049–2063 - “Urachal cysts develop when both the umbilical and bladder ends of the urachus are obliterated,
but a focal segment remains patent somewhere along the course of the urachus, more commonly at the lower third of the urachal tract. Cysts are usually small and asymptomatic.The diagnosis is often made only when they become symptomatic in childhood or adulthood because of complications, mainly infection, or as an inciden- tal finding at imaging performed for unrelated reasons .”
Imaging of the Urachus: Anomalies, Complications, and Mimics ParadaVillavicencio C et al. RadioGraphics 2016; 36:2049–2063 - “Infection represents the most common complication of urachal anomalies and may produce sometimes marked nonspecific symptoms, including abdominal pain and tenderness, fever, erythema, purulent urinary discharge, and occasionally a palpable mass. Infection routes for bacterial migra- tion can be lymphatic, hematogenous, or by direct extension from the bladder; Staphylococcus aureus is the most commonly isolated organism, fol-lowed by Escherichia coli, Enterococcus, Citrobacter, Klebsiella, and Proteus. Although it is unusual, severe infection can result in the formation of complex fistulas and abscesses, with the attendant risk of potential intraperitoneal rupture causing peritonitis and sepsis.”
Imaging of the Urachus: Anomalies, Complications, and Mimics ParadaVillavicencio C et al. RadioGraphics 2016; 36:2049–2063 - “Malignant urachal neoplasms are also rare, accounting for less than 1% of all bladder cancers.They usually remain undiscovered for a long period of time and may be found incidentally at imaging or at an advanced stage when symptoms of local invasion or systemic spread have developed.”
Imaging of the Urachus: Anomalies, Complications, and Mimics ParadaVillavicencio C et al. RadioGraphics 2016; 36:2049–2063 - “Although urachal remnants are lined by urothelium, 80% of urachal cancers are adenocarcinomas, including mucin-producing adenocarcinomas (69%) and mucin-negative adenocarcinomas (15%).The remaining 20% of urachal cancers are urothelial, squamous, and sarcomatoid neoplasms.This differs from the most common type of bladder cancer, which is typically urothelial. It is unclear why adenocar- cinoma is the predominant type, and it has been hypothesized that chronic irritation is responsible for metaplasia of the transitional epithelium into columnar epithelium.”
Imaging of the Urachus: Anomalies, Complications, and Mimics ParadaVillavicencio C et al. RadioGraphics 2016; 36:2049–2063 - “Approximately 90% of urachal carcinomas develop in the portion of the urachus adjacent to the bladder and gradually grow in the cranial direction. Cystography may reveal a filling defect
in the bladder dome or the presence of extrinsic compression.”
Imaging of the Urachus: Anomalies, Complications, and Mimics ParadaVillavicencio C et al. RadioGraphics 2016; 36:2049–2063 - “Calcifications are present in 70% of cases and are mostly seen at the periphery of the urachal mass; however, they may also be central or a com- bination of both. The presence of calcifications in a midline soft-tissue mass along the course of the urachal tract is considered pathognomonic for the diagnosis of urachal adenocarcinoma.”
Imaging of the Urachus: Anomalies, Complications, and Mimics ParadaVillavicencio C et al. RadioGraphics 2016; 36:2049–2063