Abdominal TB is defined as TB infection involving the gastrointestinal tract, peritoneum,
mesentery, abdominal lymph nodes, and solid visceral organs such as liver, pancreas
and spleen 9]. It is sixth most common type of extrapulmonary TB, affecting primarily young adults
5], 9]. It is relatively rare in children 5], 9]. While the ileocecal junction is the most common site reported for abdominal TB 10], 11], the peritoneum and lymph nodes are the most common sites involved in children with
abdominal TB 9], 12]. Mycobacterium tuberculosis and bovis (transmitted through unpasteurized dairy products)
are the main pathogens involved. The diagnosis is often delayed because of its non-specific
and protean clinical presentation 6]. It is a condition that mimics a variety of inflammatory, infectious and neoplastic
gastrointestinal diseases 9], 13]. Fever, abdominal pain and weight loss are the most common symptoms found in children
with abdominal TB 6], 12]. There are three patterns of clinical presentation depending on the predominant symptoms:
intestinal (colicky abdominal pain, vomiting and gaseous abdominal distension), peritoneal
(abdominal distension and ascites) and asymptomatic 13]. Our patient was virtually asymptomatic and had no apparent radiological features
of pulmonary TB nor clinical evidences of abdominal TB, other than the urachal discharge.
The diagnosis was established during laparoscopy performed for excision of the urachal
remnant.
Delay in diagnosis of abdominal TB is associated with high morbidity and mortality,
if left untreated 5], 14], 15]. Diagnosis is often made difficult because the signs and symptoms are non-specific
and often resemble those of other gastrointestinal diseases. It is even more difficult
in children because of the paucibacillary nature of the disease and lower culture
yields. Most children have constitutional symptoms such as fever, anorexia and weight
loss (60–70 %) 11], while some have no obvious symptoms or risk factors 12]. There are no reliable tools for the diagnosis of abdominal TB. Tuberculin skin positivity
varies from 42–88 % in different studies 11], 13], 16] and has a lower specificity for abdominal disease compared to pulmonary TB 16]. Chest radiograph is a routine and simple imaging performed but only 15–56 % of patients
with abdominal TB are reported to have chest radiographic evidence of pulmonary TB
5], 9], 16]. Ultrasound and CT imaging are important ancillary tools in the diagnosis. CT is
the most common imaging used in most studies 6], 16]. The CT features of ascites, lymphadenopathy, bowel wall thickening, or omental and
mesenteric stranding raise suspicion of abdominal TB 6], 16]. However, such findings often resemble those of bacterial peritonitis or advanced
malignant disease 5], 9], 14]. Therefore, the diagnosis of abdominal TB is often established after a correlation
of clinical features, laboratory data and imaging findings. In the era of laparoscopy,
diagnostic laparoscopy has emerged as an important diagnostic armamentarium and should
be considered when the radiological findings are ambiguous. It allows obtaining tissue
specimen for histological confirmation and ascitic fluid for acid-fast smears and
cultures 13]. It is a procedure with low morbidity and a high diagnostic yield of 70 to 95 % 10]. Peritoneal biopsy by laparoscopy has a higher diagnostic yield of 85–100 % 15] compared to 3–20 % 13] in acid-fast smears and cultures of ascitic fluid. The use of adenosine deaminase
assay in ascitic fluid improves the diagnostic yield 15] but it is expensive and not readily available. Polymerase chain reaction (PCR) testing
of the biopsied tissue is another useful tool with high specificity and sensitivity
11]. The laparoscopic approach in our case proved to be an ideal surgical approach as
it also allows treatment of the urachal remnant other than taking targeted biopsies
of peritoneal nodules under direct vision. Thus, sampling errors are minimized to
facilitate the diagnosis of abdominal tuberculosis in an unsuspected patient. In addition,
laparoscopic peritoneal biopsy results in a more rapid diagnosis of abdominal TB as
compared to conventional microbiological assays which may take up to 4–6 weeks. More
importantly, it avoids the morbidity and mortality associated with conventional laparotomy,
in particularly potential wound-related complications.
The association of abdominal TB and urachal remnants is rare. The pathogenesis of
abdominal tuberculosis in our patient was presumably via lymphohaematogenous spread
from a primary focus in the lung or ingestion of infected sputum. He most probably
had active pulmonary TB which was not radiologically apparent that subsequently spread
to the abdomen. Both the infections had remained clinically silent until the abdominal
TB manifested in the infection of urachal remnant. TB of the urachus probably resulted
from contiguous spread from an abdominal focus or mesenteric lymph node.
The urachus, a remnant of the allantois, functions to excrete urine from the bladder
via the umbilicus during the intra-uterine life of a foetus. After birth, the allantois
may fail to involute and depending on the completeness of this involution, a patent
urachus, urachal cyst, urachal sinus or vesico-urachal diverticulum may arise. Occasionally,
these structures can be infected, and prompt the diagnosis and surgical intervention.
Infection is the most common complication of urachal remnants. It is the usual mode
of presentation in an otherwise asymptomatic condition. Staphylococcus aureus is the
most common organism cultured, though other organisms have been reported. The association
of a urachal remnant and M. tuberculosis is a rare occurrence, with only two documented
case reports in a PubMed search of the English literature 7], 8].
Successful treatment of infected urachal remnants involves an initial incision and
drainage of the abscess followed by antibiotics with surgical resection best performed
after the resolution of infection and inflammation 17]. Performing a definitive surgery in the acute setting is associated with technical
difficulties and risk of injury to adjacent visceral organs, particularly the bladder
17]. Laparotomy has been the conventional method of treatment but laparoscopic approach
offers advantages of minimally invasive technique and should be preferred whenever
such expertise is available.