Teaching Case

A 71-year-old woman presented to the Emergency Department with a two-day history of vomiting and abdominal distension. She had a PEG tube in situ due to recurrent aspiration pneumonias and had a past medical history of dementia and scleroderma.
Inflammatory markers and serum lactate levels were normal.

Initial chest and abdominal plain films showed dilated loops of small bowel, pneumoperitoneum and fibrotic change at both lung bases.
IV contrast enhanced CT abdomen and pelvis showed multiple loops of dilated small bowel with extensive intramural air. A small volume of retroperitoneal and intraperitoneal free air was also identified. Of note, there was no portal venous or mesenteric venous gas and the coeliac axis and superior mesenteric artery were well-opacified with contrast.
Chest and abdominal plain films 5 days later showed resolution of the intramural gas and free air.

Pneumatosis intestinalis is defined as the presence of gas in the bowel wall and can be classified as either primary or secondary. Primary pneumatosis intestinalis radiologically and pathologically consists of cystic collections of air, usually located in the colon. Secondary pneumatosis intestinalis is characterised by linear or circumferential air in any part of the gastrointestinal tract and is associated with many clinical conditions [1].
Secondary pneumatosis accounts for approximately 85% of cases [2].
Underlying causes include mechanical/traumatic, inflammatory/autoimmune, infectious, pulmonary, drug induced and connective tissue disorders such as scleroderma [3].
The wide variety of associated conditions is reflected in the numerous terms used to refer to this phenomenon, including pneumatosis cystoides intestinalis, pneumatosis coli, cystic lymphopneumatosis and emphysematous gastritis [4].
The pathophysiology of pneumatosis intestinalis is not fully understood but two basic mechanical features characterise the majority of cases: mucosal injury, the most important and prevalent feature and increased intraluminal pressure [1]. Rupture of intramural blebs is the hypothesised source of benign pneumoperitoneum in patients with pneumatosis intestinalis, causing free air without true transmural perforation [3].
It is important to understand that pneumatosis intestinalis is a sign, not a disease and it must be interpreted relative to the patient’s overall condition [5].
Sclerodema is characterised by excessive collagen production, autoimmune disease-induced inflammation and microvascular injury [6]. The resultant pathological change consists of smooth muscle atrophy and fibrosis caused by collagen deposition in the tunica muscularis [7].
Nearly 90% of patients with scleroderma have evidence of gastrointestinal involvement, which is a substantial cause of morbidity [8].
Small bowel findings include hypomobility from smooth muscle atrophy and fibrosis, which leads to stasis, dilatation and pseudo-obstruction [6].
The clinical importance of pneumatosis intestinalis is that it may be misdiagnosed or, if identified correctly, its significance may be misinterpreted, leading to unnecessary surgical intervention [9].
In our case, the lack of portal venous gas, normal inflammatory markers and rapid clinical improvement would suggest that a diagnosis of ischaemia is unlikely.