Untitled Document

Case Report

Bull Emerg Trauma 2014;2(1):55-58.

A Late-onset Psoas Abscess Formation Associated with Previous Appendectomy: A Case Report

Sam Moslemi1*, Maryam Tahamtan2, Seyed Vahid Hosseini3

1Department  of General Surgery, Shiraz University of Medical Sciences, Shiraz, Iran
2Department  of Internal Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
3Colorectal Research Center, Shiraz University of Medical Sciences, Shiraz, Iran


Corresponding author: Sam Moslemi
Address: Department of General Surgery, Shiraz University of Medical Sciences, Shiraz, Iran. e-mail: moslemis@sums.a.ir

Received: December 7, 2013
Revised: December 15, 2013
Accepted: December 26, 2013


Please cite this paper as:
Moslemi S, Tahamtan M, Hosseini SV. A Late-onset Psoas Abscess Formation Associated with Previous Appendectomy: A Case Report. Bull Emerg Trauma. 2014;2(1):55-58.



Psoas abscesses could originate from an adjacent source of infection in the abdominopelvic cavity known as a secondary complication of acute appendicitis. However, it is considered as a very rare event when occurring late after the presentation of appendicitis. Whether it is the source or complication of acute appendicitis following appendectomy remains unclear. A 25-year-old man was admitted to our center with fever and abdominal pain. His past medical history was unremarkable except for having an acute appendicitis and complicated appendectomy 4 years before presenting illness. On admission, the patient was febrile with right lower quadrant abdominal tenderness and moderate leukocytosis. The Abdominopelvic CT- scan revealed a large right psoas muscle than the opposite site, that contained a hypodense mass measuring 6 cm in diameter with extension into right iliacus and internal oblique muscles..The patient underwent subsequent percutaneous abscess drainage under image guide and concurrent broad-spectrum antibiotic therapy.

Keywords: Late-onset psoas abscess formation; Complicated acute appendicitis; Appendectomy.



The psoas abscess is a collection of pus within the   surrounding   fascia  of   the   iliopsoas muscle [1]. It has been considered a rare entity with  a  universal  incidence of  12  new  cases per year [2]. However, the condition  has been detected  more frequently  in  recent  years [3]. There are two distinct forms of abscess formation in the psoas muscle. The primary form, known as  the  predominant   form,  originates from  a distant   source  of  infection  disseminated  via hematogenous  spread. In  the secondary form, a local infection or inflammatory process of adjacent  structures such  as vertebrae, kidneys, bowel, pancreas  and  appendix  is contagiously spread into the psoas muscle. The common underlying causes of the secondary form include appendicitis, diverticulitis, inflammatory  bowel disease, pyonephrosis, pyelonephritis and  post- operative infections. Sometimes, a neoplastic process especially of the bowel is the  primary focus leading to a psoas abscess formation [4-6]. Despite the theoretical concept of retroperitoneal perforation  of the appendix as an etiology for retroperitoneal  abscesses, the  number  of  patients reported with this condition is significantly rare [7]. The rarity of cases with a late-onset psoas abscess is highly striking, since there is only one reported case of  actiomycotic abscess of  psoas muscle detected 10 years after appendectomy [8]. The present study introduces a case with a psoas abscess appearing 4 years after appendectomy with a culture positive for E. coli.

Case Report

A 25-year-old man  from  Kangan, southern  Iran, was referred to the emergency department  of our center with a 7 days history of intermittent  fever and  progressive right  lower  quadrant   abdominal pain. The patient complained of nausea, a few episodes of vomiting and mild loss of appetite since the  presentation  of  illness. He did  not  mention any discomfort in the groin or thigh and had not experienced any difficulty in walking. Reviewing his past medical history revealed an acute appendicitis treated by open appendectomy 4 years prior to present admission documented by a pathologic report of an acute  suppurative  type without  obvious gangrene or perforation. The patient was admitted one week after the appendectomy due to surgical site infection due to incision and drainage of the site of operation and concurrent  intravenous antibiotic therapy. The physical examination revealed an ill-looking young man with no remarkable posture with the ipsilateral hip  kept  flexed. The  core  body  temperature  was 38.2 °C. The blood  pressure, respiratory  rate  and pulse rate were 120/80 mmHg, 16/min and 84 bpm respectively. He had moderate  tenderness  of right lower quadrant of the abdomen which became severe on  deep  palpation,  and,  mild  localized rebound tenderness  in  the  same area. When  extending the right hip, the patient felt much more discomfort than before. No abdominal or flank mass was detected. The lab data showed a moderate  leukocytosis (16600), predominantly   polymorphonuclear   (PMN)   cells. The other blood tests were all normal except a mild hemoconcentration corrected the day after early fluid resuscitation and empirical antibiotic therapy with a decrease in the Hb from 15.1 g/dL to 13.5 g/dL. The plain abdominal X-ray demonstrated no abnormality. In the abdominopelvic sonography, an echogenic nodule measuring 6 mm was detected in the right liver lobe  which was probably  a  hemangioma.  A hypoechoic  area  was noted  in  the  depth  of  this region. The abdominopelvic CT-scan with IV and oral contrast  revealed a larger right  psoas muscle than the opposite site which contained a hypodense mass measuring 60×40 mm, and extending into right iliacus and internal oblique muscles. The fat stranding that  extended into  the right  posterior  perinephric space was noted  in  the  above mentioned  region (Figure 1). The patient then underwent percutaneous drainage of psoas abscess and a percutaneous catheter  was placed  in  the  site  of  drainage  with concurrent  intravenous therapy by Imipenem. The culture prepared from the pus aspirate only yielded many colonies of Escherichia coli with convincing sensitivity  to   Imipenem.   Symptoms  disappeared soon  after the  percutaneous  aspiration  of  abscess and  the  patient  became afebrile after 2 days. The catheter irrigation was then discontinued and he was discharged after 5 days hospitalization in total.

Fig. 1. Axial computed tomographic scan of the abdominopelvis demonstrating a right larger psoas muscle containing a hypodense area suggestive of a psoas abscess.



The  retroperitoneal   abscess  formation   may  be a serious complication of the acute appendicitis which faces the physicians with difficult diagnosis and early treatment  due to its insidious onset and various presentations. It may be located in anywhere in the retroperitoneum  including the psoas muscle with probable extension to the thigh [7]. The etiopathogenesis of psoas abscesses has been changed over  time. Mycobacterium  tuberculosis  was  the main cause before the advent of anti-TB drugs and its control  by worldwide strategies [2]. Nowadays, Staphyloccocus aureus  is  considered  as  the  most common microorganism responsible for primary psoas abscesses [9-12]. Although the main microbial sources of the  secondary forms  has not  yet been established, the Escherichia coli is believed to be  the leading cause of primary psoas abscesses as reported by Lin MF et al., [13]. The etiology of the secondary form reflects the underlying pathologic cause, so that the enteric pathogens are incriminated as common microorganisms responsible for infection [2]. Apart from these two  bacteria, other  possible microbial etiologies involve Proteus mirabilis, Klebsiella pneumonia,  Pseudomonas  aeruginosa, Bacterioides fragilis, Serratia marcescens, Streptococcus viridians, Streptococcus epidermidis, Salmonella spp. and sometimes Brucella spp. in both primary and secondary abscesses [6,11,13-15].The most frequent manifestations of the psoas abscess include unilateral flank and lower abdominal pain and to some extent low back pain. These symptoms are accompanied by some degrees of inability to walk in some patients. In physical examination, the patient sometimes exhibits unilateral hip kept flexed due to the pain. A painful mass of the flank or lumbar region is another sign of  the  psoas muscle  involvement. There are some constitutional  symptoms and signs including anorexia, malaise and fever [12,16,17]. Because the condition  is  often  misleading, using  a  radiologic modality such as CT-scan is useful to identify the abscess, designating its characteristics and planning for the best treatment [18]. The most common finding of the CT-scan is entire enlargement of the ipsilateral psoas muscle containing a low density area which demonstrates the focus of abscess [19]. The treatment  is best established by prescribing broad- spectrum antibiotics combined with abscess drainage via open surgery or percutaneously [2].
The literature review did not show any late-onset psoas abscess formation post-appendectomy caused by E.coli. The Late-onset psoas abscess formation is reported in a few cases from 3 to 27 years after ipsilateral nephrectomy  due  to  nephrolithiasis, pyonephrosis and xanthogranulomatous  pyelonephritis [6]. Chen YC et al. reported a case with left psoas abscess whose past medical history was not significant except for an appendectomy and a cesarian section, both occurring more than 10 years prior to presenting illness [20]. The contralateral presentation of the psoas abscess and the long period since the time of appendectomy did not inspire the physicians to consider previous acute appendicitis and its complications as a probable source of present abscess. Lapus RM et al. introduced a 10-year-old boy with a retroperitoneal mass in the radiologic evaluation containing calcifications which suggested a retained appendicolith with abscess formation. The review of his past medical history revealed an  acute  perforated  appendicitis  treated by an interval appendectomy 2 years before current illness [21].  The  authors  considered  it  as  a  late uncommon  complication  of appendicitis. Another case   of   late   retroperitoneal   abscess  formation was reported  by Moosmayer S, which was within the  right  psoas  muscle  and  presented  10  years after appendectomy with pus aspirate containing Actinomyces Israeli [8]. Reviewing the literature, the reason for late appearance of psoas abscess is still unknown. It may be related to the complications of acute appendicitis such as micro-perforation causing a small abscess formation soon after the presentation of appendicitis which remains undetected until the abscess becomes large enough to make the patient symptomatic. Another leading process could originate from the complications of appendectomy including infected  hematoma  and infected  tissue remnants. However, these two likely hypotheses require further multicenter case reports in order to identify the most common pathologic process contributing to the late- onset psoas abscess formation.
In conclusion, the late-onset psoas abscess formation may be a very rare complication of acute appendicitis or a post-surgery event, especially when an enteric pathogen such as E. coli is found to be the microbial etiology of the focus of infection. The similar approach to the other psoas abscesses is required to relieve the patient from bothersome symptoms.

Conflict of Interest: None declared.



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