Abdominal wall actinomycotic mycetoma involving the bowel: a rare entity

Abstract

Actinomycotic mycetoma is a disease of the tropical region and usually presents as a chronic, suppurative and deforming granulomatous infection. We present an unusual case of actinomycotic mycetoma of the abdominal wall that was found to infiltrate into the bowel. A 51 year-old man presented with pain and swelling in the left flank of 2-year duration. Even after comprehensive preoperative evaluation with advanced radiological imaging, biochemistry and pathology, the diagnosis could not be arrived at. Histopathological examination of the excised specimen after the surgery guided to the diagnosis of actinomycotic mycetoma, which entirely changed the management in the postoperative period. We propose that mycetoma should be kept as a possible differential diagnosis for anterior abdominal wall swelling in the indicated clinical setting and the investigations be done keeping the same in mind. Otherwise, a lot of valuable time may be lost allowing the disease to progress further.

Background

Mycetoma can be caused by fungus or bacteria; if fungus is the offending agent, it is known as eumycetoma, and if bacteria is the causal organism, it is known as actinomycetoma.¹ Actinomycotic mycetoma is a distinct group of aerobic bacteria that take up the Gram stain, are non-spore bearing, react negatively to catalase and constitute a significant amount of commensal intestinal flora.² In people residing in endemic areas, mycetoma occurs most often in the foot (70%), hands (12%) and other body parts like leg, knee, head and neck, perineum and thighs.³ Occasional reports of abdominal actinomycotic mycetoma involving the viscera exists in the literature.⁴ The oldest description of this disease comes from the Byzantine period (300–600 AD); however, the first written evidence might have come from the sacred ancient Indian literature (Atharva Veda), where the reference has been made to the condition as ‘Anthill foot’.⁵

Case presentation

A 51-year-old army officer presented with complaints of pain and discomfort in the left flank of 2 years’ duration. There was no history of any urinary complaints in form of dysuria or altered frequency of micturition. The patient did not report any weight loss or any decrease in appetite. There was no history of alteration of bowel habit or bleeding per rectum. He did not recollect any episode of trauma to that area. A history of emergency open appendicectomy was present in childhood. There was no history of any coexisting medical illness. The patient gave history of tour of duty in Sudan on an army mission for the preceding 2 years. Nothing noteworthy could be elicited on the general physical examination. A note was made of well-healed McBurney’s appendicectomy scar over the right lower quadrant of the abdomen. The abdominal examination further revealed a 10×6 cm parietal mass stretching right from the lateral margin of the rectus abdominis to the anterior axillary line on the left side. There was no local rise in temperature, and the swelling was non-tender. It had limited side to side and vertical mobility. The overlying skin was healthy and unremarkable.

Investigations

The patient was evaluated with routine blood examination, including erythrocyte sedimentation rate and C reactive protein, all of which were within normal limits. Ultrasound (USG) of the abdomen showed a hyperechoic collection of the size 5×3x6 cm in the left lumbar region (figure 1). Evaluation with contrast-enhanced CT (CECT) scan revealed a heterogeneously enhancing intramuscular collection of size 5×3.2×6.5 cm with a central non-enhancing area (suggestive of necrosis) seen in the transversus abdominis muscle in the left lumbar region with adjacent surrounding fat stranding. Inflammatory changes were seen in the left paracolic space extending to descending colon with focal thickening of the colon wall. Inferiorly, the lesion was abutting the iliacus muscle superomedially reaching up to the conal fascia (figure 2). MRI showed a 5×3×7 cm hyperintense cystic lesion in transversus abdominis with perilesional oedema and enhancement (figures 3 and 4). Colonoscopy was performed to look for any communication with bowel and was reported within normal limits. Thus far, we were not able to pinpoint the diagnosis after radiological imaging. USG-guided fine-needle aspiration cytology (FNAC) was performed subsequently that showed ill-defined fragments of larva with mixed inflammatory reaction. The findings were suggestive of cysticercosis. The serology for cysticercosis yielded a serum IgG level of 1.55 (normal value <0.9). The patient received 2 weeks of medical therapy in the form of tablet albendazole 400 mg daily, but he did not show any improvement in local pain and discomfort; rather the size of the lump further increased in size by a couple of centimetres. FNAC was repeated twice after that, but the findings were only suggestive of inflammatory reaction and did not contribute towards any firm diagnosis

Figure 1.

Focused ultrasound image of the left lateral abdomen wall shows an irregular hypoechoic lesion in the transversus abdominis muscle with echogenic contents (red arrow).

Figure 2.

Contrast-enhanced CT scan axial view showing heterogeneously enhancing area in the transversus abdominis (blue arrow).

Figure 3.

Coronal post contrast T1-weighted image of the abdomen shows a peripherally enhancing lesion in the left transversus abdominis muscle with central non-enhancing area suggestive of a necrotic core (red arrow).

Figure 4.

Axial T2-weighted image of the abdomen shows a multiloculated lesion in the left transversus abdominis muscle. It shows central hyperintense signal due to liquified contents with peripheral hypointense rim due to fibrosis (red arrow).

Differential diagnosis

Initially, a diagnosis of soft tissue sarcoma was entertained, but the imaging findings were not corroborative. Cysticercosis was top on our list as the patient had a history of pork consumption, FNAC report somewhat pointing with the presence of larvae and a serology report supporting the same.⁶ However, with the subsequent FNACs that were negative for cysticercosis, a very low predilection of cysticercosis to affect the abdominal wall and moreover there was no response to the course of albendazole.⁷ At this stage, the diagnosis was still an enigma, and the discomfort of the patient as well as the size of the left flank swelling was increasing. Thus, the decision was taken to operate and explore the patient.

Treatment

The patient underwent exploration under general anaesthesia. Intraoperatively, there was a 10×10 cm lesion seen involving the transversus abdominis muscle extending to the descending colon and iliacus muscle posteriorly and the anterior superior iliac spine inferiorly. He underwent wide local excision with sleeve resection of the involved descending colon (figure 5). In the postoperative period, the patient developed surgical site infection over the incision, which subsided with daily dressings and culture-directed antibiotics. The excised specimen was found to stain positive for both Grocott and Gram stain, which pointed towards the diagnosis of actinomycotic mycetoma (figures 6 and 7). Postoperatively, patient received both oral and injectable antibiotics directed against actinomycotic mycetoma.

Figure 5.

Intraoperative picture showing transversus abdominis muscle (blue arrow), mass infiltrating colon (yellow arrow) and descending colon (green arrow),.

Figure 6.

Grocott’s stain; actinomycosis staining black in green background (red arrow).

Figure 7.

Gram staining slide showing actinomycetes taking up the stain (blue arrow).

Outcome and follow-up

The patient was asymptomatic at the time of discharge, and the surgical wound had healed well. The patient is presently on a 2 weekly follow up for the past 8 months and has remained asymptomatic. He has regained his physical fitness and has started participating in vigorous army drills.

Discussion

In our current case report, we have tried to bring forth one of the rarest clinical conditions that necessitated the multi-modality assessment preoperatively with modern imaging and intervention modalities available, yet going ahead with the surgical option when we did not have a firm clinical pointer towards the diagnosis. The literature search did not return a single case of actinomycotic mycetoma of the anterior abdominal wall extending to the colon.

Actinomycotic mycetoma primarily affects people living in the tropical climatic conditions including Africa, parts of Latin America and South eastAsia, which are popularly known as the ‘Mycetoma belt’.⁸ Sudan reports the maximum number of cases of mycetoma in the world.¹ Our patient had history of tour of duty in Sudan for the preceding 2 years where he could have acquired the infection during army drills after sustaining minor trauma or thorn prick or some other trivial injury that could have easily gone unnoticed. Minor trauma can help in letting the organism reach subcutaneous tissue from where they tend to spread to lymphatics.⁹ Actinomycotic mycetoma can spread through the bloodstream in rare instances.³ Males have three to five times increased chances of getting infected as compared with the females of a similar age group.¹ Aerobic species of actinomycetes is responsible for actinomycotic mycetoma that belong to the genera Nocardia, Streptomyces and Actinomadura, with Nocardia brasiliensis, Actinomadura madurae, Actinomadura pelletieri and Streptomyces somaliensis being the most common. Eumycetoma is caused by a wide variety of fungi such as Allesheria boydii, Madurella mycetoma, Trematosphaeria grisea, Aspergillus, Fusarium spp and Curvularia lunata among others.⁹

Mycetoma typically presents as a painless subcutaneous mass that subsequently breaks down with multiple sinuses exuding pus and clusters of bacterial or fungal colonies as grains.¹ However, the typical presentation was missing in our patient who complained of pain at the involved site and had no accompanying skin changes in the form of sinus formation. Mycetoma bears a close resemblance to Kaposi sarcoma, foreign body granuloma, malignant melanoma and sometimes even primary osteogenic sarcoma.²

The diagnosis is based on the clinical findings and is aided by examination of grains exuding out from the sinuses, which is thought to be highly specific.¹ Unfortunately, the patient did not have any available draining grains for getting a diagnosis leading to a delay in diagnosis. The grains can be of varying size, texture and colour, which helps in identifying the offending agent. The associated discharge can be subjected to culture studies. Actinomycetes grow on Lowenstein–Jensen media, thioglycolate broth, Columbia agar and brain–heart infusion agar. Incubation time with bacteria should take approximately 48–72 hours at 35°C–37°C, while the fungal counterpart requires 4–6 weeks for growth.¹⁰ Gram-stained preparation helps in distinguishing between actinomycetes and eumycetoma as only actinomycetes take up the stain while eumycetoma does not. H&E stain helps in visualising suppurative granulomas (composed of neutrophils) surrounding the characteristic grains. Actinomycetes granules show a positive reaction with Periodic-acid-Schiff and Grocott’s dye.¹¹ In our case, we too could see a positive Grocott’s staining and positive Gram staining, which helped in confirmation of diagnosis. ELISA is sensitive for the detection of circulating antibodies and has been primarily used in epidemiological studies but is less sensitive and specific for the diagnosis.⁸ X-ray and USG help to determine the extent of the disease and bony involvement, if any. There was no evidence of any bony involvement in our case. USG can help by differentiating eumycetoma and actinomycotic mycetoma based on the fact that eumycetoma exhibits bright and sharp echoes, whereas actinomycetoma grains do not appear that sharp or bright.^{2 11} CECT provides comprehensive details of visceral and soft tissue involvement. It is highly sensitive for recognising early changes.¹¹ We could not get any subtle findings suggestive of mycetoma in our imaging studies. MRI is a costly option. Still, it provides a detailed evaluation of soft tissue and bony involvement and can be handy in narrowing down the differential diagnosis of the swelling. The ‘dot-in-circle sign’ appearance is highly sensitive for mycetoma on MRI. The dots are hyperintense granulomas, and the outside area is a hypointense area that consists of fibrous tissue seen on T2-weighted imaging.¹²

The disease responds to antibiotic therapy at an early stage; however, most of the patients need surgical intervention apart from antibiotic administration.^{10 11 13} Surgery is often required for small localised lesions or to achieve better response to medical therapy after debulking the large lesions. Surgery typically varies from wide local excision to debulking the large lesions that sometimes may require even amputation of the associated limb or digit.¹ One might often underestimate the size of lesion on examination and imaging as it tends to invade deeper planes that are not apparent clinically.² The same was noted in our case as there was an extensive involvement of adjacent tissue that was not evident preoperatively. Combination regimens that are most effective in treating Actinomycotic mycetoma comprise of cyclic therapy of cotrimoxazole and amikacin sulphate. The treatment for actinomycetoma consists of amikacin (15 mg/kg/day) during 3 weeks combined with TMP-SMX (40/8 mg/kg/day) every 12 hourly for 5 weeks. One to four 5-week cycles are recommended. This cyclical therapy is popularly known as the ‘Welsh regime’.¹³ Another useful combination therapy is streptomycin and cotrimoxazole/dapsone. For those who are refractory to these antibiotics, amikacin is replaced by netilmicin and cotrimoxazole by amoxicillin-clavulanate combination. During pregnancy, treatment with only Augmentin is recommended.¹³ For eumycetoma, triazole antifungals are the treatment of choice, and usually, prolonged treatment of 1–2 years is required combined with repeated surgical debridement in case of a large-sized lesions.¹³ Actinomycetes are more responsive to treatment as compared with eumycetoma.¹ Patient should be kept on regular follow-up as there is a high chance of recurrence of the disease to the tune of 20%–50%.²

Patient’s perspective.

Initially, it started with a discomfort and constant pain in the left lower abdomen, I felt something wrong was happening with me. I attributed this to my daily exercise and strenuous army drills initially. But later I could appreciate a swelling in that area and the pain had started increasing and had great difficulty while sleeping on to my left side. I consulted many doctors and was subjected to a battery of inconclusive investigations. My anxiety kept on increasing with each passing day, kept on googling and thinking about all the enormous possibilities. Finally, I approached a surgeon who advised me surgery for my swelling to clear all the air and decided to give it a go. Things changed post-surgery although I required few additional dressings and cleaning of wound my discomfort was gone within days my wound was healed, and the thought of finally knowing about the disease made me happiest.

Learning points.

• Mycetoma should be kept as a differential diagnosis of abdominal wall swelling in an appropriate clinical setting.

• Preoperatively, establishing a diagnosis is challenging, and most of the cases are diagnosed after a careful histopathological and microbiological examination.

• Surgery is an effective means for both diagnosis and cure of the disease.

• Histopathological examination is the key to diagnosis, and pathologists should have a high index of suspicion.

• A prolonged course of antibiotics/antifungals should be given to prevent high chances of recurrence.