British Journal of Radiology (2006) 79, e1-e4
© 2006 British Institute of Radiology
doi: 10.1259/bjr/96369737
Pyourachus: study of two cases
R B Thapar, DMRD, DMRE1,
V U Jha, MS2,
R U Mehta, MD1 and
G R Shah, MS, MCh2
Departments of 1 Radiology and 2 Urology, Sir Hurkisondas Nurrotamdas Hospital & Research Center, Raja RamMohan Roy Road, Mumba-400004, India
Correspondence: Dr Ravikumar B Thapar, 302, Amar Residency, Punjabwadi, S.T.Road, Deonar, Mumbai – 400088, India.
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Abstract
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The urachus, or median umbilical ligament, is a midline tubular structure that extends upward from the anterior dome of the bladder toward, the umbilicus and represents the vestigial remnant of at least two embryonic structures, the cloaca and the allantois. The tubular urachus normally involutes before birth, remaining as a fibrous band, however its persistence can give rise to various clinical problems, not only in infants and children but also in adults. We report two cases of pyourachus at our institute with a review of the clinical presentation, imaging findings and surgical management. Both our patients were young males, with haematuria being the presenting feature in one case which has not been previously described in literature.
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Introduction
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The urachus is a vestigial remnant of the cloaca and the allantois which is present after birth as a midline fibrous cord extending from the anterior dome of the urinary bladder to the umbilicus. The abnormal persistence of the urachal patency may result in various clinical problems at any age. Due to their rarity, these urachal remnant diseases are frequently misdiagnosed and confused with a wide spectrum of midline intra-abdominal or pelvic disorders. A detailed understanding of the embryological basis of these urachal disorders and their imaging features is crucial for the correct diagnosis and management. We report two cases of pyourachus at our institute with a brief review of the embryology, anatomy, clinical presentation, imaging findings and surgical management.
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Case reports
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Case 1
A 19-year-old male, with a known case of stricture urethra at the bulbomembranous junction, presented to our institute with pain and fullness in the suprapubic region for the last 3 days. The routine blood investigations revealed a total leukocyte count of 12 800 cm–3 and an elevated serum creatinine of 3 mg dl–1. The patient then underwent ultrasound of abdomen and pelvis, which revealed bilateral hydronephrosis and hydroureter with a well localized collection above the dome of the bladder, immediately beneath the anterior abdominal wall. This collection showed internal echoes suggestive of turbid contents (Figure 1
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Figure 1. Ultrasound of the pelvis showing a well localized hypoechoic collection indenting the bladder dome.
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The contrast enhanced computed tomography (CECT) scan of abdomen and pelvis revealed bilateral hydronephrosis and hydroureter with a well localized, thick walled, rim enhancing collection in the suprapubic region extending from the anterior dome of the bladder to the umbilicus with adjacent fat stranding (Figure 2). The central portion of the collection had attenuation value of around 45 Hounsfield units. The delayed and prone scans after bladder opacification did not reveal any communication between the bladder and this collection. The anatomical location of this collection correlated with the course of the urachus which was well demonstrated on the sagittal multiplanar reconstruction (MPR) images (Figure 3) and, hence, a diagnosis of infected collection within the urachal remnant (Pyourachus) was suggested.
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Figure 2. (a) Contrast enhanced CT (CECT) scan at the level of bladder dome showing a thick walled, rim enhancing collection related to the anterosuperior aspect of the bladder. Note the relatively high density of the collection as compared with the urine in the bladder, suggestive of infected turbid contents. (b) CECT scan at the level of the umbilicus shows the heterogeneously enhancing collection with adjacent fat stranding extending up to the umbilicus.
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Figure 3. Sagittal multiplanar reconstruction(MPR) image delineates the classical "cone-shaped" anatomical extent of the collection along the course of the urachus with its tip at the umbilicus and the base over the bladder dome.
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The patient underwent a cystoscopy with visual internal urethrectomy (Cysto VIU) for the urethral stricture. The cystoscopy revealed a grossly trabeculated bladder with an extrinsic indentation on the superior wall showing petechial haemorrhages. A small opening was seen but could not be negotiated. Laparotomy was then performed at the same sitting and the abscess cavity was dissected from umbilicus to the bladder and excised en bloc, along with a cuff of the bladder wall (Figure 4). The histopathology report confirmed the diagnosis of urachal abscess.
Case 2
A 25-year-old male presented with complaints of haematuria and burning micturation over the past 9 days and fever with chills for 3 days. He had a past history of pulmonary Koch's and had been on anti-tuberculous chemotherapy for 3 months. The blood investigations revealed a total leukocyte count of 6300 cm–3, elevated erythrocyte sedimentation rate (ESR) of 64 mm and a normal serum creatinine of 1.1 mg dl–1. Routine urine examination showed 80–100 RBCs / hpf and 10–12 pus cells / hpf. The frontal chest radiograph revealed bilateral hilar adenopathy.
Ultrasound of the abdomen and pelvis was then performed, which showed a 2 cm x 2 cm mixed echogenic polypoidal lesion in the fundus of the bladder. No evidence of calcification was seen. CECT scan of abdomen and pelvis revealed a focal necrotic nodular lesion involving the anterosuperior wall of the urinary bladder, projecting into the anterior perivesical space and the bladder lumen (Figure 5). There was no evidence of calcification or lymphadenopathy. The kidneys and ureters were normal. Considering the location and morphology of the lesion, a differential diagnosis of infected urachal remnant or an urachal neoplasm was considered.
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Figure 5. Contrast enhanced CT scan at the level of the bladder shows a focal, heterogeneously enhancing, nodular lesion along the anterosuperior aspect of the bladder.
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Cystoscopy revealed an indentation on the dome of the bladder with petechial haemorrhages in the overlying mucosa (Figure 6). The patient was taken up for laparotomy. The urachus was identified and traced to the mass, which was excised en bloc along with the urachus and 1 cm margin of the bladder. The histopathology analysis revealed an urachal cyst abscess with no evidence of malignancy or tuberculosis.
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Figure 6. Cystoscopy showing an indentation on the bladder dome with petechial haemorrhages in the overlying mucosa.
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Discussion
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The urachus is an embryonic remnant resulting from the involution of the allantoic duct and the ventral cloaca [1]. The obliterated urachus, also known as the median umbilical ligament, extends from the anterior dome of the bladder towards the umbilicus. It measures 3–10 cm in length, 8–10 mm in diameter and lies between the transversalis fascia and the peritoneum, in the space of Retzius. The urachus is encased between the two layers of the umbilicovesical fascia, which tends to contain the spread of urachal disease. The urachus is a muscular tube, and three distinct tissue layers are recognized: (1) an epithelial canal with transitional (70%) or columnar (30%) epithelium; (2) a submucosal connective tissue layer; and (3) an outer layer of smooth muscle that is in continuity with the detrusor muscle and thickest near the bladder [2]. However, once the urachus becomes a fibrous cord, the urachal layers are generally not recognizable.
The urachal remnant diseases may be classified as congenital urachal anomalies and acquired urachal remnant diseases which include infection and neoplasm. The congenital urachal anomalies are twice as common in males as in females and 4 types are recognized [3].
1. patent urachus (about 50% of cases);
2. urachal cyst (about 30% of cases);
3. urachal sinus (about 15% of cases); and
4. urachal diverticulum (about 5% of cases).
Patent urachus is usually recognized in the neonate due to discharge of urine through the umbilicus which may occasionally be minimal or intermittent. It is associated with urethral atresia or obstructive posterior urethral valves in 15–30% of patients, in whom it serves as a protective mechanism [4]. However, the other congenital urachal anomalies are generally asymptomatic, the clinical presentation being usually associated with a superadded infection [5].
An urachal cyst develops if the urachus closes both at the umbilicus and at the bladder, but remains patent between these two areas. It develops most commonly in the distal third of the urachus and the majority of them are infected at the time of diagnosis. Therefore, they usually present with lower abdominal pain, fever, voiding symptoms, midline hypogastric tenderness, palpable mass and evidence of urinary infection [2]. Haematuria as a presentation of urachal cyst as seen in case 2 is very rare. Infected cysts occur more commonly in adults and only occasionally in children. Non-infected urachal cysts may become symptomatic when they enlarge or may be detected incidentally during routine examination.
In an excellent review of urachal remnant diseases, Yu et al have detailed the spectrum of CECT and ultrasound findings [5]. The preferred method of diagnostic imaging is ultrasound, which will show a fixed, midline, cystic, extraperitoneal mass between the umbilicus and the bladder [5]. If there is superadded infection, ultrasound will demonstrate wall thickening, internal debris and complex echogenicity. The CECT characteristics of infected urachal cyst or pyourachus include (a) midline location deep to the rectus abdominis muscle; (b) conical shape extending from a tip at the umbilicus to a base over the bladder dome; (c) peripheral inflammatory changes in subcutaneous tissues, rectus abdominis muscle and mesenteric fat; and (d) intraperitoneal fluid or abscess (if perforation has occurred) [7]. The attenuation of the purulent cyst contents will be higher than that of water. MRI does not usually provide any significant additional information while intravenous urography and voiding cystourethrography may only show an extrinsic impression on the fundus of the bladder.
CT or ultrasound guided diagnostic percutaneous aspiration may be performed. However, this does not play a therapeutic role due to the high recurrence rate. The organism most commonly cultured from the cyst fluid is Staphylococcus aureus [8].
The infected urachal cyst may drain along the urachus and result in acquired forms of urachal sinus (drainage through the umbilicus), urachal diverticulum (drainage through the bladder), or alternating sinus where drainage shifts alternately between the umbilicus and the bladder. If the drainage is at the umbilicus, a fistulogram in the lateral view is preferable, while if drainage at the bladder is suspected, a cystogram in the lateral view will better reveal the disease [4]. Other serious complications of an infected urachal cyst include rupture into the peritoneal cavity causing significant peritonitis and, rarely, inflammatory involvement of the adjacent bowel and formation of an enteric fistula [9].
Besides infection, other complications of an urachal cyst include urinary retention, haemorrhage and an increased incidence of adenocarcinoma. If a cyst harbouring a mucinous adenocarcinoma ruptures, pseudomyxoma peritoneii may result [10].
The complex echogenicity at ultrasound and heterogeneous attenuation and contrast enhancement on CECT may cause confusion between an infected urachal remnant and urachal carcinoma, as in case 2. Urachal carcinomas are usually mucinous adenocarcinomas and show punctate, stippled or peripheral curvilinear calcification in 50–70% of cases [11]. The presence of haematuria, mural nodularity and calcification at CECT, along with lack of adjacent inflammatory change, help to differentiate urachal malignancy from an infected cyst [5]. In such cases, where imaging is unable to differentiate these two entities, CT or ultrasound guided percutaneous needle biopsy or fluid aspiration is mandatory for diagnosis and therapeutic planning.
The management of an urachal cyst is usually surgical. Primary excision is the treatment of choice for uninfected cyst. In case of infected cysts, either a one stage excision or two stage drainage with subsequent total excision including a cuff of bladder may be performed. The two-staged approach helps to limit the amount of bladder wall resected and reduces the risk of injury to the adjacent intraperitoneal structures [2]. Total excision of the cyst wall is essential to eliminate the risk of future reinfection and carcinoma. Recently, endoscopic approach for the excision of urachal cyst has been described [12].
Received for publication January 14, 2005.
Revision received May 1, 2005.
Accepted for publication June 27, 2005.
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References
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Abstract
Introduction
