(1655) Diffuse Pneumocephalus From Rectothecal Fistulization in Setting of Metastatic Rectal Adenocarcinoma

Introduction: This case discusses a unique manifestation in a patient with metastatic rectal adenocarcinoma that resulted in rectal abscess ultimately causing fistula formation and facilitating creation of pneumocephalis and pneumorrhachis.

Description: A 48-year-old male patient with a history of stage four colorectal adenocarcinoma with liver and lung metastases was brought to the emergency department after a cardiac arrest. He was intubated prior to presentation at the hospital. At time of admission, he was febrile to 101.7F, and tachycardic to 102 with a blood pressure of 102/75mmHg on an intravenous infusion of norepinephrine.  Laboratory investigations were remarkable for a white blood cell count of 33,200/uL with 84% neutrophils, c-reactive protein of 225mg/L, erythrocyte sedimentation rate > 130mm/h, and procalcitonin 12.39ng/mL. The patient was started on empiric broad spectrum antibiotics.

A non-contrasted computed tomography (CT) of the head showed large volume pneumocephalus along the bifrontal extra-axial space and subarachnoid pneumocephalus within the basal cisterns. A CT of the chest, abdomen, and pelvis demonstrated large volume intrathecal air throughout the spinal canal (Pneumorrhachis). It also showed irregular thickening of rectal walls consistent with the known malignancy and multiple loculated, gas-containing fluid collections adjacent to the rectum consistent with rectal perforation with formation of multiple abscesses invading into the presacral fat (1). Based on these findings, fistulation of the presacral abscess to the spinal canal resulted in purulent infection and large volume pneumocephalus and pneumorrhachis.

Discussion: These conditions of air in the spinal column and brain occur more often in the setting of trauma or neurosurgical interventions and are occasionally described following an endoscopy (2,3,4). Pneumorrhachis has also been reported with lumbar punctures and pneumothorax (1). However, pneumocephalus and pneumorrhachis caused by a metastatic rectal adenocarcinoma resulting in rectal abscess and causing fistualization is very rare, and to the degree of pneumocephalus and pneumorrhachis as seen in this case.