depending on the location of the perforation , signs of peritoneal irritation may be evident in cases of intra - peritoneal free perforation but hidden in cases of retroperitoneal perforation . the abscess or colonic gas may spread via various anatomic pathway when perforation of diverticulitis in the retroperitoneum occurs , and diverse atypical clinical symptoms may be present . thus , the atypical manifestation of retroperitoneal perforation of diverticulitis can cause difficulties when making the diagnosis . the delayed diagnosis and treatment could result in high morbidity and mortality . pneumomediastinum is initiated by many precipitating factors or diseases . however , it is rarely associated with colonic perforation , particularly in patients with no history of colonoscopic procedure [ 3 - 6 ] . here a 59-year - old man was referred to the emergency department because of persistent abdominal and left flank pain . the left flank pain had started 30 days before this visit as an acute nephrolithiasis . he had visited the local clinic and presumptive impression was left ureter stone because left costovertebral angle ( cva ) tenderness was apparent although radiologic study was not performed . however , the left flank pain worsened and was accompanied by abdominal pain 1 week ago . on physical examination , the patient looked ill and had a temperature of 38.2 , the blood pressure was 90/40 mmhg , the pulse rate was 101 beats / min , and the respiratory rate was 24 breaths / min . the abdomen was slightly distended and tender over the lower abdomen , without signs of generalized peritoneal irritation . laboratory results were within the normal range , except for the white blood cell count of 21,000/l . chest x - ray showed scanty bilateral pleural effusion without pneumomediastinum or free air in the peritoneal cavity ( fig . however , a computed tomography scan showed an infiltrative mass in the descending colon involving the left para - renal space . in addition , it showed massive air bubbles in the left retroperitoneum with diffuse infiltrates into the soft tissue ( fig . an emergency operation was performed because of suspected diverticulitis or colon cancer perforation with abscess formation . during the operation , a colonic diverticulitis perforation over the posterior wall of the sigmoid descending junction and a retroperitoneal abscess with necrosis of the parietal peritoneum were found . a segmental resection of the diseased colon and end colostomy were performed ( hartmann 's procedure ) . post - operative culture of the drain revealed enterococcus faecalis , which were sensitive to various antibiotics including penicillin , vancomycin , erythromycin , ciprofloxacin , and gentamicin . thus , we added vancomycin instead of metronidazole to the previous empirical antibiotics ( 1st generation cephalosporin , gentamicin , metronidazole ) on the 4th post - operative day . however , the condition of the patient deteriorated progressively after operation . colonic diverticulosis is a common disease , and its incidence increases with aging . among the patients with colonic diverticulosis , approximately 20% may develop diverticulitis as a result of infection and inflammation of the diverticuli . the perforation of diverticulitis is one of the most serious complications that require an urgent operation . the perforated lesion is usually covered and leads to abscess formation , whereas free perforation into the peritoneal cavity leading to diffuse peritonitis is relatively rare . in cases of free perforation , the diagnosis of diverticulitis perforation may be difficult depending on the location of the perforation , e.g. , perforation into the retroperitoneal space . in such cases , its manifestation can be presented with various conditions , including thrombophlebitis of the leg , inguinal abscess , hip and buttock pain , subcutaneous emphysema , and shortness of breath [ 1,3 - 6 ] . these various pathologic conditions caused by diverticulitis perforation can be explained by considering the anatomy . meyers   reported that if gas is present in the para - renal space , which can be caused by sigmoid diverticulitis perforation , its progression from the posterior para - renal space through the diaphragm hiatus results in pneumomediastinum and cervical subcutaneous emphysema . reported that the soft tissue compartment of the neck , thorax , and abdomen contains four regions defined as the subcutaneous tissue , prevertebral tissue , visceral space , and previsceral space . the visceral space extends from the neck through the mediastinum to the retroperitoneum , forming an anatomic connection between these areas . therefore , an abscess or colonic luminal gas caused by diverticulitis perforation into the retroperitoneal space can spread to the other areas , resulting in unusual manifestations , similar to those observed in our case . the unusual complications of diverticulitis perforation have been reported , e.g. , subcutaneous emphysema , cellulitis , necrotising fasciitis , pneumopericardium , pericarditis , pneumothorax , and pneumomediastinum [ 1,3 - 6 ] . it can be caused by traumatic injury , intrathoracic infections , excessive coughing , sneezing , and in rare cases , colonic perforation , which is associated with a complicated colonoscopic procedure . to the best of our knowledge , there have been 5 cases of pneumomediastinum as a sequence of diverticulitis perforation in english literature ( table 1 ) . in these cases , the main symptoms were abdominal pain and fever , which were often accompanied with subcutaneous emphysema [ 3 - 6 ] . the symptoms and clinical signs of retroperitoneal diverticulitis perforation may be unclear and nonspecific at an early stage , and complications may occur without any previous symptoms of diverticulitis . therefore , making the correct diagnosis could be delayed and difficult , like in our case . in concusion , pneumomediastinum caused by retroperitoneal diverticulitis perforation is a very rare manifestation , and the symptoms are unclear . this leads to a delayed diagnosis , which can cause a life - threatening condition , particularly in patients without signs of peritonitis . it is necessary to consider the possibility of a colonic origin in patients presenting with abdominal pain and showing findings of pneumomediastinum for the prompt management of this condition .
a 59-year - old man presented with abdominal and left flank pain . 
 the symptom had started 30 days before as an acute nephrolithiasis , which had worsened despite conservative management . the abdomen was slightly distended and tender over the lower abdomen , without signs of generalized peritoneal irritation . 
 a computed tomography ( ct ) scan showed an abscess in left para - renal space up to the subphrenic space and an unexpected pneumomediastinum . 
 an emergency operation was performed , which showed retroperitoneal diverticulitis perforation of the sigmoid descending junction with abscess formation . 
 a segmental resection of the diseased colon and end - colostomy was performed ( hartmann 's procedure ) . 
 however , the patient 's condition progressively deteriorated , and he died of sepsis and multi - organ failure on the 5th postoperative day . although pneumomediastinum caused by colonic diverticulitis perforation is extremely rare , it could be a life - threatening condition in patients without signs of peritonitis because of delayed diagnosis .