Tuberculosis (TB) still remains a major public health issue all around the world, despite the fact that the World Health Organization declared it a global health emergency twenty years ago. According to the Global Tuberculosis Report, about 10.4 million people developed TB in 2015, and 95% of the cases were reported in developing countries. In recent years a decline in TB-related deaths has been observed. However, worldwide, TB represented the first cause of mortality from infectious diseases in 2015, with around 1.4 million registered deaths. TB is classified along with HIV as leading causes of mortality from infectious diseases.¹

Epidemiology

Based on Romanian Tuberculosis Notification Data, 12,498 new TB cases (a rate of 6.4 cases per 100,000 individuals) were registered in our country during 2014, which is higher compared with a rate of 5.2 cases per 100,000 individuals throughout Europe.² Extrapulmonary involvement occurred only in 8% of the new cases. Among the extrapulmonary TB (EPTB) cases, the most interested anatomical sites were as follows: lymph nodes (30.1%), osteoarticular (13.3%), genitourinary (6.3%) and other various organs (47.3%).²

Although it is well known that TB occurs mainly in immunocompromised hosts, it seems that TB prevalence has increased both in immunocompetent and immunocompromised patients.³ Between 2002 and 2011, EPTB accounted for 19.3% of all TB cases throughout Europe, ranging from 5.5% to 44.4%.⁴Pelvic TB is common in developing countries, mainly in young, fertile women aged between 15 to 25 years old.⁵ In particular, peritoneal TB (PTB) is the sixth most common location of EPTB, with an incidence between 0.1% and 0.7% of all TB cases worldwide. Moreover, the rate of new PTB cases is increasing in developed countries due to immigration.⁶

Clinical picture and diagnosis challenges

The diagnosis of PTB is difficult due to the nonspecific clinical manifestations, being often confused with adnexal tumors in the presence of ascites. The symptoms depend on patient age, physical status and comorbidities. The most common clinical feature is ascites (73%), followed by abdominal pain (64.5%), weight loss (61%), fever (59%), abdominal tenderness (47.7%), hepatomegaly (28.2%), splenomegaly (14.3%) and bowel disorders such as diarrhea (21.4%) or constipation (11%).⁷ In addition, the diagnosis of EPTB may be challenging due to the paucibacillary biological samples, which partly explains the lower sensitivity of bacteriological tests. Thus, Ziehl-Neelsen staining from ascites fluid samples is positive in less than 3% of cases, while the culture is positive in less than 20% of cases.⁸ According to the National Institute for Health and Care Excellence (NICE) guideline from 2016, the main tests for the diagnosis of TB remain microscopy, culture and histology, although these are difficult and time-consuming methods.⁹Currently, the polymerase chain reaction (PCR) detection of Mycobacterium tuberculosis (MTB) deoxyribonucleic acids (DNA) is the most widely used diagnostic method, providing higher sensitivity and advantage of detection of genetic mutations associated with rifampicin.¹⁰ At the moment, the accurate diagnosis of PTB is based on peritoneal biopsy with detection of MTB-DNA from the tissue specimens. One of the key issues of this method is related to the invasiveness of the procedures, such as laparoscopic guidance, minimum laparotomy or exploratory laparotomy.¹¹ Therefore, the PTB diagnosis requires new methods, which ideally should be widely available, inexpensive, less invasive, and with higher sensitivity and specificity.

Case report

A 15-year-old young female patient presented at the territorial hospital with abdominal distension, low abdominal pain, fever (40 °C) with shivers, excessive sweating and loss of appetite. No other previous health problems were reported. All vaccines provided in the universal vaccination schedule had been performed. She denied smoking, drug use or alcohol consumption, and she was sexually inactive. The tests performed led to the diagnosis of ascites of unknown etiology. Despite empirical antibiotic treatment with ceftriaxone, she continued to present fever, being subsequently referred to our clinic for further investigations.

At admission, the clinical status of the patient revealed a relatively good general condition, without fever, no abnormalities on pulmonary examination and normal vital signs. The abdomen was enlarged, with shifting dullness and positive ascitic wave, diffuse pain on palpation, without signs of peritoneal irritation. No masses or organomegaly were present on clinical examination.

Blood tests showed lymphopenia (880/cmm), mild microcytic anemia, elevated inflammatory markers (erythrocyte sedimentation rate of 58 mm/1h, fibrinogen of 709 mg/dL, C-reactive protein of 112 mg/dL) with negative procalcitonin and normal biochemistry. Chest X-ray did not reveal any infiltrates. Abdominal ultrasonography showed the ascites in large quantity. Transthoracic echocardiography described minimal pericardial effusion (20-30 millimeters). Further immunology and virology laboratory tests (rheumatoid factor, anti-double stranded DNA antibodies (Ab), antinuclear Ab, complement fractions C3, C4, hepatitis B surface antigen, hepatitis C virus Ab, and human immunodeficiency virus 1 and 2 Ab) were negative. The patient underwent paracentesis with ascitic fluid analysis. The gross appearance of the fluid was pale yellow, with exudative features, based on the biochemistry. Biochemistry results showed a serum-ascites albumin gradient < 1.1 g/dL, normal glucose level (68 mg/dL) and high lactate dehydrogenase level (1,815 IU/L). The cytology, after lysing red blood cells with acetic acid, revealed a total nucleated cell count of 600/cmm with predominance of polymorphic lymphocytes (72%). The ascites fluid adenosine deaminase (ADA) level reached a high value of 140 IU/L, normal values being <33 IU/L. The microscopy for non-specific bacteria and acid fast bacilli, using Gram and Ziehl-Neelsen stains, was negative. Moreover, we performed a broad-spectrum molecular microbial identification from the ascites fluid (IRIDICA BAC BSI® Assay platform for bacteria and fungi) and MTB-DNA amplification (GeneXpert® platform), both tests yielding undetectable results. Serum tumor markers such as CEA, CA19-9 and CA15-3 were within normal limits, apart from CA-125, which was significantly higher (189.5 IU/mL). Serum gamma-interferon specific to MTB antigens produced by T cells (QuantiFERON®-TB Gold) was positive.

After admission in our clinic, we started empiric antibiotic treatment based on oral clarithromycin 1 g/day for 3 days, with fever persistence. Then we switched to intravenous (iv) ertapenem 1 g/day. After 5 days of ertapenem treatment, the fever has disappeared, with minimal ascites fluid regression. Abdominal and pelvic magnetic resonance imaging (MRI) showed the presence of ascites and described irregular masses with peripheral contrast enhancement near the ovarian fossa, similar to epiploic fringes.

The patient was transferred to a pediatric general surgery department for exploratory laparoscopy and peritoneal biopsy. The laparoscopic findings described thickened peritoneum with disseminated miliary white nodules on the surface and intestinal wall congestion, being highly suggestive of PTB (Figure 1). Multiple tissue biopsies were collected.

Figure 1. Laparoscopic findings with thickened peritoneum, diffuse congestion, disseminated miliary white nodules on the surface of peritoneum, and "stalactite-like” structures highly suggestive for TB

The histopathological results confirmed the diagnosis of peritoneal tuberculosis (Figures 2 and 3). In addition, MTB-DNA from the biopsy sample was detected, with no detection of genetic mutations associated with rifampicin resistance.

Figure 2. Multiple foci of granulomatous inflammation with multinucleated giant cells, epithelioid histiocytic cells and peripheral lymphocytes are seen on Periodic acid–Schiff (PAS) staining (100X)

 

 

Tuberculosis is one of the most common chronic infectious diseases. Its prevalence is on the rise in immunocompetent but also in immunocompromised patients and it can affect virtually any organ. Delay in diagnosis and treatment initiation leads to poor prognosis and sequelae in up to one fourth of cases.^3,12

Pulmonary TB is easily diagnosed and confirmed by sputum examination. On the contrary, in EPTB the diagnosis is quite difficult and challenging because of nonspecific symptoms and low sensitivity of classical diagnostic methods, such as microscopy and culture. About 15-25% of EPTB coexist with pulmonary forms; therefore, the diagnosis might be established by sputum examination and chest X-ray.⁸ In our case, the chest X-ray had no signs of tuberculous lesions.

Abdominal TB is one of the most prevalent forms of EPTB and peritoneal involvement has been observed in about 1-2% of all cases of TB. Most cases of tuberculous peritonitis are a result of reactivation of latent TB foci.⁷PTB can evolve in three different forms: wet-ascites, fibrotic-fixed and dry-plastic form, the former being the most frequent.⁸ The common clinical features include ascites, fever, diffuse abdominal pain and weight loss. Therefore, PTB is often misdiagnosed, usually as carcinomatous peritonitis.⁵ The lack of medical awareness of PTB could lead to mutilating surgical treatment like adnexectomy for many young, fertile, women.¹¹

Our patient presented with a clinical picture highly compatible with PTB. However, we had to continue the investigations in order to rule out the other causes of ascites, such as malignancy or autoimmune diseases, cirrhosis, heart failure, nephrotic syndrome. Based on clinical data, laboratory tests and abdominal MRI we were able to exclude the majority of the differential diagnoses, except for intraabdominal malignancy, because of elevated levels of ascitic ADA and serum CA-125 marker.Since 1978, ADA has been used in the diagnosis of tuberculous effusion, yet high levels of ADA have been reported also in non-infectious conditions such as malignancies (adenocarcinoma, leukemia, lymphoma) or collagen vascular disease (systemic lupus erythematosus, rheumatoid arthritis).¹³

CA-125 is also elevated in other conditions such as endometriosis, ovarian hyperstimulation, active hepatitis, pericarditis, acute pancreatitis and commonly in ascites and pelvic TB, making the diagnosis more difficult.⁵

In patients with PTB, the ascitic fluid has exudative features with serum ascites albumin gradient below 1.1 g/dL, a high lymphocyte count, elevated LDH, decreased glucose level, and ADA levels >35 IU/L.⁸

In our case, given the ascitic fluid characteristics, in correlation with ADA ascites level of 140 IU/L and serum CA-125 level of 189.5 IU/mL, there was a high suspicion of PTB.

ADA catalyzes the enzymatic conversion of adenosine and deoxyadenosine to inosine and deoxyinosine. Tuberculous effusion is the result of a cellular immune response to MTB antigens from peritoneal tuberculi and is characterized by the accumulation of activated T cells and macrophages. ADA can also be a marker of cellular immunity in general and T cell activation in particular.¹²It is known that ADA level in pleural fluid has proven useful for the diagnosis of pleural TB. In addition, there are studies that proved the benefit of ADA quantification in cerebrospinal, pericardial or peritoneal fluids for the diagnosis of TB. Therefore, ascitic ADA levels have been recommended for use as a rapid diagnostic method for tuberculous peritonitis.¹⁴ The main problem when using ADA in the diagnosis of PTB is related to determining the cut-off value in the ascitic fluid, to guide clinical decision. In a meta-analysis on 4 articles and 264 patients of which 50 had PTB, cut-off values of ADA levels within 36 to 40 IU/L showed 100% sensitivity and 97% specificity. ADA values over 56 IU/L were associated only with TB. In particular cases, patients with PTB and cirrhosis or HIV infection may have ADA levels lower than the cut-off values.⁶ It has been shown that an ADA cut-off level of 21 IU/L yields the best results for differential diagnosis between PTB and peritoneal carcinomatosis, showing better discriminative power than tumor markers.¹⁵

Today, serum CA-125 is considered another biomarker useful for the diagnosis of TB. There are many reports from Germany, Japan and Turkey that showed that CA-125 may be increased in patients with TB-associated pleural effusion. Moreover, the level of CA-125 significantly decreases after one to two months of antituberculous treatment.¹⁶ A cross-sectional study that included 30 patients with the clinical suspicion of PTB has compared ascitic fluid ADA and serum CA-125 in diagnosing of PTB. All patients had histopathological confirmation of PTB by laparoscopic peritoneal biopsy. The results showed that at a cut-off value of 24 IU/L for ADA, and 34 U/mL for CA-125, respectively, both biomarkers had high sensitivity and specificity (93%, 96% for ADA and 98.4%, 95.9 % for CA-125, respectively).

The studies showed a significant correlation between ADA and CA-125 in patients with PTB. The tests are simple, non-invasive, cheap, and seem to have enough power to confirm or exclude the diagnosis of peritoneal tuberculosis and it is a good approach to begin empirical treatment while waiting for the histopathological result or cultures.¹⁷

Use of the GeneXpert® MTB RIF assay has considerably grown over the recent years. Although PCR detection of MTB from tissue samples showed 74.1% sensitivity and 96.1% specificity, detection from ascites fluid samples showed poor sensitivity.^18,19 In our case MTB-DNA amplification from ascites fluid was undetectable, thus it was not helpful.

The imaging techniques are considered useful for the diagnosis of PTB. The ultrasonography features of PTB are intraabdominal free or loculated fluid, fluid collections in the pelvis that can mimic an ovarian cyst, "club sandwich” or sliced bread sign and lymphadenopathy.²⁰ Computed tomography (CT) findings can describe lesions in the omentum, mesentery, peritoneum and mesenteric lymph nodes suggestive of PTB. However, these characteristics may not be enough to allow distinguishing PTB from ovarian carcinoma or peritoneal carcinomatosis.⁴ Given the age of our patient, we decided to perform an MRI which confirmed the presence of ascites fluid and irregular masses near the ovarian fossa related with epiploic fringes. Nevertheless, the imaging findings in our case were unspecific.

Nowadays, the diagnosis of PTB is based mainly on invasive techniques like laparoscopic biopsy. A diagnosis of PTB is often suggested by characteristic findings at laparoscopy or laparotomy such as stalactite-like fibrinous masses in the parietal peritoneum.⁸ Visual diagnosis during surgery classifies the laparoscopic appearance of the disease into three types, according to Bhargava criteria: miliary nodules, ascites and peritoneal features. Typically, the microscopy describes the presence of epithelioid granuloma with caseation or identifies acid-fast bacilli. Combining macroscopic appearance and histopathological results, the sensitivity and specificity rates vary from 85% up to 95%, respectively 98%.⁷ However, these are invasive examination methods and should be used with caution in clinical practice.

In patients with a nonspecific clinical picture of ascites with exudative features, a high ascites fluid ADA level, in the absence of imaging suggestive of malignancy, could be highly indicative of PTB, irrespective of serum CA-125 level and undetectable result of MTB-DNA from ascites samples.

In addition to clinical-biological findings and radiological characteristics, the accuracy of early diagnosis may be increased by measuring the ascites ADA and serum CA-125 levels, especially in cases where the conventional methods, like microscopy and MTB-DNA amplification from ascitic fluid, fail to establish the positive diagnosis. Moreover, in particular cases, when patients refuse invasive procedures such as exploratory laparoscopy and biopsy, or the clinical condition does not allow such investigations, ascitic ADA and serum CA-125 levels may be useful tools to guide the decision to defer or start antituberculous treatment, and to monitor the evolution.

Tuberculosis still remains a worldwide public health issue, affecting also immunocompetent hosts in developed countries. Thus, in young, fertile women presenting with large febrile ascites, often mimicking adnexal malignancy, surgeons should be aware of PTB, avoiding unnecessary mutilating surgery leading to increase in PTB complications, such as infertility.