Langerhans cell histiocytosis (LCH) is a group of idiopathic disorders characterized by the proliferation of specialized, bone marrow-derived langerhans cells and mature eosinophils. The clinical spectrum ranges from an acute, fulminant, disseminated disease called Letterer-Siwe disease to solitary or few, indolent and chronic lesions of the bone or other organs called eosinophilic granuloma. Involvement of the gastrointestinal tract is very rare in LCH. We present the case of a 53-year-old woman referred by her primary care physician for a screening colonoscopy. A single sessile polyp, measuring 4 mm in size, was found in the rectum. Histopathological examination revealed that the lesion was relatively well circumscribed and comprised mainly a mixture of polygonal cells with moderate-to-abundant pink slightly granular cytoplasm. The nuclei within these cells had frequent grooves and were occasionally folded. Immunohistochemical staining was positive for CD-1a which confirmed the diagnosis of LCH. On further workup, there was no evidence of involvement of any other organ. On follow up colonoscopy one year later, there was no evidence of disease recurrence. Review of the published literature revealed that LCH presenting as solitary colonic polyp is rare. However, with the increasing rates of screening colonoscopy, more colonic polyps may be identified as LCH on histopathology. This underscores the importance of recognizing this rare condition and ensuring proper follow-up to rule out systemic disease.

Pulse oximetry is a widely used technique in biomedical optics, but currently available pulse oximeters rely on empirical calibration approaches, which perform poorly at low saturations. We present an exact solution for pulse oximetry and show how this can be used as the basis for the development of a semiempirical calibration approach that may be useful, especially at low saturations and variable probe geometries. This new approach was experimentally tested against traditional empirical calibration techniques on transmission pulse oximetry for monitoring of fetal sheep using a minimally invasive spiral probe. The results open the way for the development of more accurate pulse oximetry.

Acute esophageal necrosis (AEN) also known as “black esophagus” or necrotizing esophagitis is a rare syndrome characterized by a striking diffuse patchy or circumferential black appearance of the esophageal mucosa that preferentially affects the distal esophagus and terminates at the gastroesophageal junction. Only 88 patients over a span of 40 years have received this diagnosis, and the prevalence of this disease ranges from 0.001 to 0.2% of cases in literature. It more commonly affects men (4 : 1 ratio) in the sixth decade of life. It is associated with a high mortality rate, approaching 32%. We report a case of AEN presenting in the setting of diabetic ketoacidosis (DKA), affecting both the proximal and distal esophagus.

Jejunogastric intussusception is an uncommon but potentially life-threatening complication of a previous gastrojejunal anastomosis. Although jejunogastric intussusception was first described in 1914, fewer than 200 cases have been reported in the English literature thus far. Awareness of this rare complication would help in early diagnosis and appropriate management. Described here is a case report of a patient who presented with hematemesis due to an acute jejunogastric intussusception associated with gangrene of the intussuscepted jejunum.