pneumoperitoneum , the presence of free air within the peritoneal cavity outside of the viscera , results from perforation of intra - abdominal organs in 90% of cases .
approximately 515% of pneumoperitoneum cases are not due to intra - abdominal organ perforation but are the result of thoracic , gynecologic or other intra - abdominal pathologies .
thoracic injuries leading to pneumomediastinum have several etiologies , arising predominantly from mechanical ventilation - induced barotrauma , but it can also occur after cardiopulmonary resuscitation , pneumothorax , tracheal rupture , median sternotomy and blast injury .
the flow of air from the thoracic cavity to the abdomen is a result of pressure differences , and intrathoracic pressures of 60 cm h2o or greater will result in subcutaneous emphysema and pneumoperitoneum from progression of air flow [ 3 , 4 ] .
of 233 patients , 32 were positive for free air on radiograph ; of which , 25 had a gastric perforation managed surgically .
another seven patients were without a hollow viscus intra - abdominal injury , though all had pneumothorax in common and the majority had other intra - abdominal injuries .
an 82-year - old male with past medical history of diabetes mellitus and alcohol abuse arrived by ambulance after being found unresponsive at the bottom of a flight of stairs with a scalp laceration . while en route to the hospital
, two unsuccessful intubation attempts were made for a glasgow coma scale ( gcs ) of 8 . upon arrival in the emergency department ( ed ) ,
his gcs was determined to be 3 and was intubated with use of the glidescope .
physical examination revealed decreased breath sounds on the left and crepitus over the left chest wall , suggestive of subcutaneous emphysema , and an immediate tube thoracostomy was performed prior to chest x - ray ( cxr ) to reduce the suspected pneumothorax .
cxr post chest tube placement demonstrated large amounts of subcutaneous emphysema ( fig .  1  )
, which was also visible on computed tomography ( ct ) scan along with evidence of pneumomediastinum and pneumoperitoneum ( fig . 
2 ) , with pneumoretroperitoneum and pneumoperitoneum present on abdominal ct scan ( fig .  3 ) . as a result of the fall , he also sustained a fracture of the right frontal bone , fractures of the c2 and c3 vertebrae , and mild subarachnoid and subdural hemorrhage without shift .
he was admitted to the surgical intensive care unit ( sicu ) and maintained on mechanical ventilation , remaining hypotensive , hypothermic and mildly tachypneic , becoming increasingly unstable over the next 8 h. due to the known pneumomediastinum , pneumoperitoneum and worsening instability , he was taken to the operating room for suspected viscus perforation and peritonitis .
an exploratory laparotomy was performed , which revealed air within the lesser sac , but no evidence of bleeding or perforation .
when closing the operative site , crepitus was also noted over the right chest wall , and a chest tube was placed into the right pleural space . 

figure  1:cxr performed after thoracostomy and chest tube placement displaying areas of subcutaneous emphysema ( white arrows ) . 
 figure  2:chest ct scan obtained shortly after patient 's arrival displaying evidence of subcutaneous emphysema ( white arrow ) , pneumomediastinum ( black arrow ) and air tracking down resulting in pneumoperitoneum ( gray arrow ) . 

figure  3:sagittal view from ct abdomen / pelvis with contrast ( a ) showing areas of free air in mediastinum and thoracic cavity spreading downward into peritoneum ( white arrows ) .
pockets are visible around the aorta , pancreas and liver ( white arrows ) , as well as the presence of subcutaneous emphysema .
cxr performed after thoracostomy and chest tube placement displaying areas of subcutaneous emphysema ( white arrows ) .
chest ct scan obtained shortly after patient 's arrival displaying evidence of subcutaneous emphysema ( white arrow ) , pneumomediastinum ( black arrow ) and air tracking down resulting in pneumoperitoneum ( gray arrow ) .
sagittal view from ct abdomen / pelvis with contrast ( a ) showing areas of free air in mediastinum and thoracic cavity spreading downward into peritoneum ( white arrows ) .
pockets are visible around the aorta , pancreas and liver ( white arrows ) , as well as the presence of subcutaneous emphysema .
postoperatively , the patient was rapidly weaned from all vasopressor agents , though he required persistent mechanical ventilation .
he developed several complications including acute respiratory distress syndrome , pneumonia and acute renal failure with ongoing hyponatremia .
after 22 days in the sicu , the patient 's family elected to pursue inpatient hospice care as the patient remained on mechanical ventilation and was generally non - responsive .
in our case , a fall caused a rib fracture that resulted in a lung laceration , leading to a pneumothorax .
the macklin effect occurs when traumatic rupture of alveoli causes free air to travel along bronchovascular sheaths .
however , in the setting of pneumothorax and pneumomediastinum , the intrathoracic pressure may be higher than intra - abdominal pressure .
this pressure reversal forces free air from the thoracic cavity into the intra - abdominal cavity , resulting in pneumoperitoneum .
two other reports describe pneumothorax progressing to pneumomediastinum and pneumoperitoneum after a fall [ 5 , 6 ] , whereas the majority of other reported cases were due to higher - energy traumas than our patient 's fall [ 5 , 7 , 8 ] .
our patient had a tube thoracostomy performed on arrival in the ed , which should have released any accumulated intrathoracic pressure prior to developing pneumomediastinum and pneumoperitoneum .
other reported cases have theorized that delayed placement of the chest tube was responsible for the pneumoperitoneum , making this case unique in that regard .
diagnosis of pneumoperitoneum is often only possible with imaging , initially on plain radiographs or by ct scans .
some have advanced the idea of nonsurgical treatment of spontaneous pneumoperitoneum in the absence of a pathological condition that necessitates surgical exploration .
hoover et al . produced an algorithm suggesting proper management of spontaneous pneumoperitoneum ( fig . 
4 ) , basing their primary recommendations for management on radiologic imaging , temperature , leukocyte count and physical examination .
our patient was hypothermic , had a leukocyte count within normal limits and was unresponsive , so a proper abdominal examination could not be performed . per this algorithm surgical exploration
however , our patient had worsening hypotension , tachycardia , hypothermia , tachypnea , acidosis with high anion gap and hypokalemia , and we felt it was pertinent to progress to laparotomy due to his decline in status . though laparotomy did not reveal any perforations , the patient 's vital signs normalized postoperatively over the next 24 h. 
 figure  4:adaptation of the algorithm initially proposed by hoover et al .   for managing spontaneous pneumoperitoneum .
adaptation of the algorithm initially proposed by hoover et al .   for managing spontaneous pneumoperitoneum .
pneumoperitoneum in the absence of hollow viscus perforation is uncommon , and even rarer when caused by low - impact traumatic pneumothorax without concomitant abdominal trauma .
similar cases have resulted from higher - impact trauma that allowed for the accumulation of greater intrathoracic pressures or delay in tube thoracostomy .
the combination of low - impact trauma and immediate tube thoracostomy does not favor the development of pneumothorax progressing to pneumomediastinum and pneumoperitoneum , making this case unique .
the development of subsequent hemodynamic instability has not previously been described , raising the possibility that even in the absence of intra - abdominal injury , releasing pneumoperitoneum via laparotomy may be beneficial .
while surgical management is not necessary for all cases of pneumoperitoneum , due to our patient 's worsening status , an exploratory laparotomy was warranted and was ultimately therapeutic .
 here , we present a case of pneumoperitoneum caused by traumatic pneumothorax after a fall . 
 the patient is an 82-year - old male who was brought into the emergency department after being found at the bottom of a flight of stairs with a bleeding scalp laceration . upon presentation , 
 the patient underwent emergent intubation followed by tube thoracostomy placement , had necessary imaging and was transferred to the surgical intensive care unit ( sicu ) . 
 imaging revealed signs of pneumomediastinum and pneumoperitoneum in addition to the partially resolved pneumothorax . in the sicu , 
 the patient became hemodynamically unstable requiring vasopressor support , which in the face of documented pneumoperitoneum without a clear cause mandated exploration . 
 he was taken to the operating room for suspected viscus perforation , though none was found after extensively searching during an exploratory laparotomy . 
 we suspect the patient developed pneumomediastinum and pneumoperitoneum as a result of traumatic pneumothorax , hastened by his subsequent intubation and mechanical ventilation . 