Pyomyositis as an Unusual Presentation of Colonic Adenocarcinoma

Abstract

Introduction:

Pyomyositis has been described in association with hematological malignancies. It is rarely associated with solid cancers, particularly colorectal carcinoma. Colorectal carcinoma can present with local or systemic abscesses by causing perforation of the colonic mucosa, followed by local or hematogenous spread of infection.

Case Presentation:

A 68-year-old male with a history of hypertension and type II diabetes mellitus presented to the emergency department with a 3-day history of left thigh pain. Magnetic resonance imaging of the thigh showed extensive intramuscular edema in the left thigh adductor and psoas muscles consistent with pyomyositis. An urgent debridement and irrigation of the left thigh revealed pan-sensitive Escherichia coli and Streptococcus viridans. Due to the suspicion of a gastrointestinal or genitourinary source of infection, computed tomography of the abdomen and pelvis showed an apple-core lesion along the mid-distal segment of the descending colon. Colonoscopy and biopsy confirmed the diagnosis of colonic adenocarcinoma. The patient underwent a laparoscopic left hemicolectomy with an end colostomy and was started on an adjuvant chemotherapy regimen with no significant side effects.

Conclusion:

Colorectal carcinoma can be associated with local or systemic abscess formation. When cultures from an abscess show enteric pathogens, it is essential to look to gastrointestinal or genitourinary tracts for the source of infection. Although rare, the diagnosis of pyomyositis should warrant further investigations to unmask the possible underlying cause.

Background

Pyomyositis is defined as a pyogenic skeletal muscle infection, which was first described as an infection of healthy individuals living in tropical areas.¹ However, in the Western world, it has been described in association with immunosuppressive states such as HIV, malignancies, and rheumatological diseases.^1,2 Acute lymphoblastic leukemia is the most common reported malignancy with pyomyositis.¹ A MEDLINE search revealed only two reported cases of colorectal carcinoma (CRC) presenting with pyomyositis.^3,4 CRC has been described to be associated with local and systemic abscess formation. The infection mechanism is likely related to colonic perforation, followed by the extension of infection to the surrounding tissues, or hematogenous spread, leading to distant abscesses.^5,6 The incidence of perforation in CRC is 3-10%; thigh abscesses complicate 0.3-4% of these perforations.⁷

This case report was prepared following the CARE Guidelines.⁸

Case Narrative

A 68-year-old male with a history of hypertension and type II diabetes mellitus presented to the emergency department with a 3-day history of a severe left thigh and hip pain. He described the pain as dull, aching, limiting his physical activity, and associated with subjective fevers and chills at home. He also reported generalized fatigue for the past 2 weeks. His home medications included metformin, insulin glargine, atorvastatin, and lisinopril. He denied recent changes in his medications, apart from insulin glargine that was added 2 months ago. Vital signs were significant for tachycardia with heart rate 106/minute and fever of 101°F (38.3°C). Physical examination was notable for the tenderness and a macular rash on the anteromedial aspect of the left thigh. Laboratory studies (Table 1) showed leukocytosis, microcytic anemia, elevated erythrocyte sedimentation rate, C-reactive protein, and creatinine phosphokinase. An ultrasound of the left leg was negative for deep venous thrombosis. Radiography of the left hip and femur was negative for fractures. The patient was started on intravenous clindamycin in addition to aggressive intravenous hydration. However, he continued to have continuous pain and fever while on antibiotics. Magnetic resonance imaging (MRI) of the left hip was done to rule out septic arthritis and showed extensive intramuscular edema in the left thigh adductor, psoas, and vastus medialis muscles consistent with pyomyositis (Figure 1). An urgent debridement and irrigation of the left thigh was performed, and the fluid’s culture revealed pan-sensitive Escherichia coli and Streptococcus viridans. During the surgery, it was noted that the pus was present between the adductor brevis and magnus muscles extending to the femur’s lesser trochanter and up to the psoas tendon. Based on the culture results, we had a high suspicion of gastrointestinal or genitourinary origin of the abscesses. A computed tomography (CT) of the abdomen and pelvis was done and showed an apple-core lesion along the mid-distal segment of the descending colon with surrounding fat stranding and nodularity (Figure 2).

Table 1.

Laboratory results at time of admission

Labs	Time of admission	Reference values
WBCs	18.3	4.0-12.0 10 × 3/µL
Hemoglobin	9.3	12.6-16.5 g/dL
MCV	77	80-100 fL
Platelets	513	150-400 10 × 3/µL
ESR	> 100	0-15 mm/h
CRP	26.5	0.0-1.0 mg/dL
CPK	495	0-200 U/L

WBCs = white blood cells; MCV = mean cell volume; ESR = erythrocyte sedimentation rate; CRP = C-reactive protein; CPK = creatinine phosphokinase.

Figure 1.

MRI left thigh, axial T2 fat suppression, showing severe intramuscular edema around the adductor musculature (arrows).

Figure 2.

CT abdomen and pelvis with contrast, coronal view, showing apple-core lesion along the mid-distal segment of the descending colon along with wall thickening and fat stranding (arrows).

Colonoscopy showed a 50 mm malignant-appearing mass in the descending colon (Figure 3). Biopsies of the mass exhibited moderately to poorly differentiated colonic adenocarcinoma (Figure 4). Immunohistochemistry showed a loss of Postmeiotic segregation Increased 2 (PMS2) and high levels of microsatellite instability. A CT of the chest revealed no evidence of metastatic disease. He underwent a laparoscopic left hemicolectomy with an end colostomy. During the procedure, the mass was found adherent to the retroperitoneum with colonic perforation and abscess cavity.

Figure 3.

Colonoscopy showing malignant appearing mass in the descending colon.

Figure 4.

Pathology showing moderately to poorly differentiated colonic adenocarcinoma.

One week later, the patient was discharged to a sub-acute rehabilitation center on intravenous piperacillin-tazobactam. After recovering, he was started on adjuvant chemotherapy, including fluorouracil, leucovorin, and oxaliplatin (FOLFOX regimen) as an outpatient.

Eighteen months after this admission, the patient underwent reversal of the colostomy and finished six cycles of chemotherapy, which he tolerated well without significant side effects. A repeat CT of the abdomen and pelvis showed postoperative changes with no evidence of recurrence. A timeline of the case appears in Table 2.

Table 2.

Timeline of the case

08/19/2018	Patient presented with left hip and thigh pain, associated with fever and chills for 3 days. Labs showed leucocytosis, elevated procalcitonin, CRP, and CPK.
08/20/2018	Patient reported no improvement while on intravenous clindamycin with persistent elevation of WBCs. Left lower limb duplex ultrasound negative for DVT.
08/21/2018	Orthopedics evaluated the patient, and an MRI of the hip and femur was ordered to rule out septic arthritis.
08/22/2018	MRI showed pyomyositis and multiple abscesses, and urgent debridement and drainage with wound vacuum placement was done. Antibiotics were switched to piperacillin-tazobactam and vancomycin.
08/23/2018	Cultures showed pan-sensitive Escherichia coli and Streptococcus viridans. Infectious disease service recommended a CT of the abdomen and pelvis due to the enteric organisms in the culture. Antibiotics were de-escalated to piperacillin-tazobactam.
08/24/2018	CT of abdomen and pelvis showed an apple-core lesion in the descending colon. Gastroenterology service proceeded with colonoscopy that showed 50 mm malignant mass in the descending colon.
08/25/2018	General surgery proceeded with laparoscopic hemicolectomy and end colostomy.
08/26/2018	Biopsy results showed ulcerated invasive adenocarcinoma. Medical oncology was consulted.
08/27/2018	Oncology recommended adjuvant chemotherapy with FOLFOX regimen after the patient recovered from his surgical wounds.
09/01/2018	Patient discharged to a subacute rehabilitation center. Infectious disease recommended 10 days of piperacillin-tazobactam.
11/13/2018	Patient had port placement and was started on chemotherapy in the form of FOLFOX regimen.
06/30/2019	Patient underwent reversal of colostomy.
02/25/2020	Patient is currently on day 1 of cycle 6 of chemotherapy. He is tolerating chemotherapy with no major side effects. Repeat CT scan of the abdomen showed postoperative changes with no evidence of recurrence.

CRP = C-reactive protein; CPK = creatinine phosphokinase; WBCs = white blood cells; DVT = deep venous thrombosis.

Discussion

Pyomyositis was first described in 1885 as a skeletal muscle infection in tropical areas.¹ In the Western world, it was described in immunocompromised individuals such as patients with HIV, intravenous drug use, diabetes, malignancies, or rheumatological diseases.^1,2 Pyomyositis is uncommon, with approximately 330 reported cases in the US between 1981 and 2004.⁹ Among these 330 cases, the majority of HIV-negative pyomyositis cases were associated with diabetes mellitus, and only 12 cases were described to be associated with solid malignancy.⁹ Upon review of the literature, pyomyositis was found to be more associated with hematological malignancies than solid tumors.² Among hematological malignancies, acute lymphoblastic leukemia was the most common, either as the first presentation or in the relapsed settings.² A MEDLINE search revealed only two cases of CRC presenting with pyomyositis.^3,4 Lower extremity muscles, mainly the thigh, were found to be the most common site of pyomyositis.⁹ Fever, muscle pain, and local swelling are the most common clinical presentations. Elevated creatinine phosphokinase is uncommon in pyomyositis and is estimated to involve < 5% of the cases.⁹ Cultures and microbiological analyses provide additional information on the source of infection.¹ Falgas et al. reviewed 44 patients with pyomyositis associated with hematological malignancies; Staphylococcus aureus was found to be the most common organism (60% of the cases).² In cases where cultures grow enteric pathogens, it is crucial to consider the genitourinary and/or gastrointestinal tracts as sources of infection.¹⁰ Hence, further imaging studies such as CT of the abdomen and pelvis might be warranted. Pyomyositis can be diagnosed by ultrasound, MRI, or CT. Treatment of pyomyositis involves surgical drainage, appropriate antibiotics, and treatment of any underlying causes.⁹

CRC can present with local or systemic abscesses.^5,6 The tumor outgrows its blood supply causing necrosis and perforation of the colonic wall with bacterial translocation and abscess formation.³ The hematogenous bacterial spread can lead to systemic abscesses.⁵ Impaired immunity in cancer patients favors the formation of abscesses, primarily when associated with immunosuppressive states such as diabetes in our case.^5,6 The incidence of perforation in CRC is 3-10%; thigh abscesses complicate 0.3-4% of these perforations.⁷ Surgical management of CRC cases complicated by local abscesses is associated with 50% mortality and 5-year survival rates of 20%.⁷

The apple-core lesion is the classic radiological sign of CRC causing colonic stricture, it is typically described on barium enema but can also be seen on abdominal CT.¹¹ Differential diagnosis of apple-core lesion in the colon includes CRC, Crohn’s disease, ulcerative colitis, lymphoma with colonic involvement, intestinal tuberculosis, and other types of colitis.¹²

Our patient did not have any symptoms suggestive of colon cancer; however, he reported a change in his bowel habits 2 months before the presentation that was attributed to recent changes in his diabetic regimen. He also had uncontrolled diabetes with hemoglobin A1c of 9, which is an additional risk factor for developing pyomyositis. He never had a colonoscopy and had microcytic anemia on admission, which was likely a result of the underlying malignancy.

Conclusion

Pyomyositis is a rare presentation of solid malignancy, particularly colorectal carcinoma (CRC). When cultures grow enteric pathogens, clinicians should direct their attention to the gastrointestinal and/or genitourinary tracts looking for the source of infection.