Emphysematous cystitis is a potentially life-threatening condition characterized by the amassing of gas within the wall of the bladder, as a result of infection by gas-forming organisms. However, the amassing of gas in the wall of the bladder does not always result from an infectious etiology. Here we report the case of a patient diagnosed with lung cancer and treated with chemotherapy, where there was air within the bladder wall accompanied by pneumoperitoneum. The presence of an infectious etiology was not clear, and the patient responded successfully to medical treatment. Although emphysematous cystitis is the most common diagnosis, the presence of gas within the wall of the bladder is a sign and not a disease per se. In our opinion, the case displays similar characteristics to those of pneumatosis cystoides intestinalis, and for this reason we refer to it as bladder pneumatosis.