Case report

Background

Managing infectious complications after kidney transplantation (KT) continues to be a significant challenge. Infections are the most common non-cardiovascular cause of death among kidney transplant recipients (KTr). The urinary tract is particularly prone to infections in this group, leading to high rates of morbidity, mortality, and substantial economic costs. In this case report, we describe for the first time an unusual complication: extensive thigh pyomyositis resulting from cystic fistulae caused by anaerobic bacterial infection in an 84-year-old KTr.

Case presentation

An 84-year-old male was referred to our hospital following an acute onset of fever (39.5 °C), pain in the inner thighs and pyuria after returning from Mauritania. He had undergone a KT in May 2018 due to focal segmental glomerulosclerosis. His medical history included prostatic adenocarcinoma in 2008, which was treated with hormone therapy and radiotherapy, resulting in radiation cystitis and rectitis. His immunosuppressive treatment regimen included anti-thymocyte globulin induction and maintenance therapy with tacrolimus, mycophenolic acid and corticosteroids. His lowest serum creatinine level was 140 µmol/L. Post-transplant complication was only marked by cytomegalovirus reactivation.

Prior to the onset of thigh pain and fever, the patient reported urinary symptoms and significant fatigue. He presented with pain in the inner thighs, which was exacerbated by passive leg movements and restricted leg mobility, though no neurological deficits were noted. Clinical examination revealed extreme tenderness in the right and left thigh adductor and gluteal muscles, but there was no crackling, fluctuation or crepitus upon palpation. The examination of the area showed no skin inflammation or lymphadenopathy. Pyuria was noted on initial examination and worsened following abdominal and thigh physical examination (e.g., pressure applied to the abdomen or thighs).

Blood tests revealed anemia with a hemoglobin level of 8.6 g/dL, a normal platelet count (224000 cells/mm³), hyperleukocytosis with a white blood cell count of 18800 cells/mm³, predominantly neutrophils (89%), and an elevated C-reactive protein level of 148 mg/L. Additionally, a non-obstructive acute kidney injury was noted, with serum creatinine levels rising to 250 µmol/L. Urine culture identified Finegoldia magna and Enterococcus faecalis, while initial and follow-up blood cultures were negative.

A thoracic-abdominal-pelvic CT-scan revealed bilateral pyomyositis of the thighs with multiple abscesses in the adductor muscles and hydroaerobic levels (Fig. 1).

Fig. 1
figure 1

Adductors pyomyositis: Contrast enhanced computed tomography with axial and coronal Views: multiple bilateral muscular abscesses involving the adductor compartments (arrow) with heterogeneous hydro-gaseous content (asterisk). Note the muscular and soft tissue effusion and fascia perimuscular thickening (arrowhead)

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The scan also showed a cystic fistula complicated by pubic symphysis osteitis, characterized by a fistulous tract between the antero-inferior wall of the gallbladder and the symphyseal disk, cortical erosions and a heterogeneous appearance of the pubic bone (Figs. 2 and 3)

Fig. 2
figure 2

Pubic symphysis osteitis: Computed tomography with axial (A), coronal (B) and sagittal (C and D). Views: cortical erosion (arrow) with heterogenous pattern of the medulla (asterisk). Note the pathological fracture of the right ischio-pubic ramus (arrowhead)

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Fig. 3
figure 3

Cystic fistulae: Contrast enhanced computed tomography with axial (A) and sagittal (B). Views: fistulous tract (arrow) with hydro-gaseous content (asterisk) between the anterior and the inferior wall of the gallbladder and the symphyseal disk

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Due to the presence of multiple abscess pockets, radiological drainage was deemed impractical, necessitating bilateral surgical drainage. Perioperative bacteriological samples isolated Finegoldia magna, Enterococcus faecalis, and Lactobacillus gasseri. Finegoldia magna was sensitive to penicillin G, cefoxitin, and metronidazole but resistant to clindamycin. Both Enterococcus faecalis and Lactobacillus gasseri were sensitive to penicillin G. Empirical broad-spectrum antibiotic therapy was initiated with intravenous meropenem and vancomycin for 48 h, followed by amoxicillin/clavulanic acid for four weeks instead of amoxicillin in the event of the presence of anaerobic bacteria not detected by blood samples.

A cystectomy with Bricker ileal conduit urinary diversion and curettage of the pubic symphysis were recommended. However, the patient was deemed too frail and advanced in age for surgery. Consequently, he has experienced recurrent urinary tract infections, primarily due to the Enterococcus faecalis strain, for which palliative treatment with amoxicillin has been initiated.

Conclusion and discussion

We present the first documented case of kidney allograft pyelonephritis complicated by bilateral inner thigh pyomyositis, resulting from cystic fistulae with pubic symphysis osteitis and perineal soft tissue infection. Pyomyositis is a bacterial infection of the skeletal muscles, initially identified in tropical regions, typically leading to abscess formation and often associated with gram-positive organisms [1]. Radcliffe et al. reported a high prevalence of Staphylococcus species (62%), as well as Streptococcus species, while gram-negative and anaerobic bacteria are relatively rare [2]. In KTr, pyomyositis caused by anaerobic pathogens such as Finegoldia magna and Lactobacillus gasseri is uncommon. Finegoldia magna is typically associated with osteoarticular infections, particularly prosthetic joint infections [3, 4].

Treatment guidelines for pyomyositis depends on the infection’s stage [5]. Early-stage infections generally respond well to conservative antibiotic therapy [6]. Once abscesses have formed, incision, debridement, and drainage, along with antibiotic treatment, may be necessary [6]. Surgery is usually reserved for abscesses that are inaccessible to radiologic percutaneous drainage [6]. With timely and appropriate treatment, complete healing without long-term complications is usually achieved [4].

In this case, the link between pyelonephritis, cystic fistulae, and bilateral thigh pyomyositis is strongly suggested. The patient initially presented with pyelonephritis, reported urinary symptoms and fatigue a few days before developing thigh pain. Additionally, Finegoldia magna and Enterococcus faecalis were identified in both the thigh abscess and urinary samples, while abdominal and thigh pressure exacerbated the pyuria. Biliary leakage involvement is unlikely, as no gallbladder leakage was detected on the thoracic-abdominal-pelvic CT scan, and blood tests showed no evidence of hepatic cytolysis or major cholestasis. Clinical examination also showed no signs of cholecystitis (Murphy’s sign was negative).

In kidney transplant recipients, lower limb pyomyositis due to urinary tract infections is extremely rare and significantly worsens the overall prognosis of these patients.