RETCHING IN PNEUMONIA: AN UNCOMMON PRESENTATION OF A COMMON PROBLEM

Abstract

SESSION TITLE: Medical Student/Resident Chest Infections Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Retching is defined as periodic, forceful, spasmodic contraction of the muscles of the diaphragm, abdomen and chest wall without the expulsion of the contents of the stomach. It often occurs as a precursor to vomiting. Here we present the case of a patient presenting with retching as his only symptom, the cause was deemed to be community acquired pneumonia. CASE PRESENTATION: A 60-year-old man with a 40-pack-year smoking history presented with 4 days of severe retching. He described this as dry heaving, the sensation of vomiting with nothing coming up. He denied any cough, fever, chest pain or vomiting. Labs were significant for a WBC of 19,700/mL, and a serum sodium of 126mEq/L. Remaining serum electrolytes were normal. Urine sodium was 24mEq/L and urine osmolality was 307mOsm/kg. CT chest showed a 7.5 x 3.6cm focal opacification in the right upper lobe (fig 1). The patient was started on Piperacillin/Tazobactam with a plan to biopsy the lesion if there was no improvement. He was given Prochlorperazine which led to immediate improvement, with complete resolution of retching by day 4. A Repeat CT done after completion of a 10 day course of antibiotics (fig 2) showed some improvement. Follow up CT at 6 months (fig 3) showed complete resolution. DISCUSSION: Retching is a prelude to vomiting and involves contraction of the diaphragm and intercostal muscles with a closed glottis to reduce intrathoracic pressure while abdominal wall muscles contract to increase intra-abdominal pressure. The lower esophageal sphincter remains closed preventing ejection of gastric contents. The physiologic pathway of the emetic reflex is not completely understood, but it involves afferent input to the brainstem centers like solitary tract nucleus and the chemoreceptor trigger zone (CTZ) via the vagus, glossopharyngeal, trigeminal and phrenic nerves. This leads to stimulation of the vomiting center. Impulse then travels to the nucleus ambiguus, dorsal motor nucleus of the vagal nerve, and the ventral respiratory group leading to the aforementioned muscular action associated with retching. In the index patient we hypothesize that the inflammatory response associated with pneumonia led to irritation of the vagus and phrenic nerves causing persistent retching. This is supported by the improvement of symptoms after administration of prochlorperazine, which works via suppression of the CTZ. Further, there was complete resolution of retching after treatment with antibiotics. The patient’s smoking history, hyponatremia due to SIADH, and the presence of a large mass raised concerns for malignancy, as such biopsy was planned if lesion did not improve after antibiotic treatment. CONCLUSIONS: Evaluation of the thorax with imaging is prudent in patients presenting with retching as inflammatory, infectious or malignant lesions can cause this symptom via stimulation of the afferent limbs of the vagus or phrenic nerves. Reference #1: Quigley EM, Hasler WL, Parkman HP. AGA technical review on nausea and vomiting. Gastroenterology. 2001;120(1):263-86. Reference #2: Nair J, Streeter KA, Turner SMF, et al. Anatomy and physiology of phrenic afferent neurons. J Neurophysiol. 2017;118(6):2975-2990 Reference #3: Babic T, Browning KN. The role of vagal neurocircuits in the regulation of nausea and vomiting. Eur J Pharmacol. 2014;722:38-47 DISCLOSURES: No relevant relationships by Muhammad Faiz, source=Web Response No relevant relationships by Jovan Gayle, source=Web Response No relevant relationships by Somshukla Ghosh, source=Web Response No relevant relationships by Moises Matos, source=Web Response No relevant relationships by Jose Urdaneta Jaimes, source=Web Response