VOMITING

Vomiting, i.e. forceful expulsion of gastric contents with nausea or retching, is a protective reflex, controlled by central emesis centers, which should be differentiated from regurgitation-an effortless involuntary event without nausea or retching.

Emesis ce ntres are located in medulla and stimulated either directly by neurogenic afferents from GIT or indirectly by chemical stimuli from nearby chemoreceptor trigger zone (CTZ). Efferent response involves sudden violent descent of diaphragm and contraction of abdominal muscles to increase intra-abdominal pressure, with relaxation of cardiac sphincter to expel gastric contents.

Etiology: Occasional episodes of self-limiting vomiting are common in infancy due to possetting, overfeeding or aerophagia. A vomiting is likely to be pathological in presence of following Red-flag signs-(a) persistent or recurrent vomiting, (b) associated diarrhea, constipation or abdominal pain/distension, (c) associated fever, respiratory distress, altered sensorium or seizures, or

(d) presence of bile or blood in vomitus (Table 14.3).

Diagnostic evaluation aims to identify the etiology as well as consequences of vomiting, e.g. dehydration, dyselectrolytemia and growth failure in persistent/ recurrent cases. Metabolic alkalosis with hypochloremia is commonest electrolyte abnormality due to loss of acidic gastric juices in vomiting. Important diagnostic clues include:

• Age of onset: Vomiting in newborns is a warning for congenital gut anomalies or neonatal sepsis after excluding benign causes, e.g. possetting, aerophagia or overfeeding. Infants with recurrent vomiting must be investigated for GERD, pyloric stenosis and inborn

GER: Gastroesophageal reflux; IHPN: Infantile hypertrophic pyloric stenosis; NEC: Necrotizing enterocolitis; CIBD: Chronic inflammatory bowel diseases; ICSOL: Intracranial space occupying lesion; RDS: Riley-Day syndrome; CAH: Congenital adrenal hyperplasia; IEM: Inborn errors of metabolism

errors of metabolism. In older children, viral or drug- induced gastritis is the leading cause of vomiting apart from surgical abdominal emergencies, viral hepatitis, CNS infections, urinary tract infections, etc.

• Onset and course: Sudden onset of vomiting is usually due to local causes, e.g. viral or drug-induced gastritis or intestinal obstruction; while recurrent/persistent episodes indicates systemic pathology, e.g. raised intracranial pressure (ICP), hepatorenal disease or metabolic disorders. Recurrent vomiting with normal intervening period may also suggest cyclical vomiting syndrome or abdominal migraine.

• Force, e.g. forceful projectile vomiting indicates raised ICP or pyloric stenosis.

• Diurnal/postural variations, e.g. early morning vomiting episodes may be due to raised ICP, while tendency to vomit in recumbent position indicates possible GERD.

• Relation with feeds: Vomiting during or immediately after feeds indicates esophageal obstruction, while a delay of 15-20 minutes is common in pyloric stenosis. Vomiting due to extra-intestinal causes is not related to feeds.

• Contents: Presence of undigested food or fresh blood indicates upper GIT pathology, while bile indicates post-duodenal obstruction. Vomitus is highly foul­smelling in colonic obstruction and may contain fecal matter. Persistent, large, watery vomiting may also be due to rare Zollinger-Ellison syndrome.

• Preceding/comorbid events, e.g. headache, infection, drug ingestion, dietary intake, worm infestation, diarrhoea/constipation, foreign body and similar family history (food poisoning, migraine, metabolic defects) provide vital diagnostic information.

• Physical examination helps in etiological diagnosis, with presence of icterus in viral hepatitis, abdominal tenderness in surgical causes, neurological signs or papilledema in raised ICP; as well as to assess complications, e.g. dehydration, electrolyte disturbances, failure to thrive. Failure to thrive indicates chronic cause, e.g. infections, subacute obstruction and metabolic disorders.

Relevant investigations are necessary for etiological diagnosis as well as to assess fluid and electrolyte status. Important investigations in persistent vomiting include- urine analysis, liver/renal functions tests and abdominal ultrasonography, followed by CSF examination, eso- phagoscopy and metabolic screening in selected cases.

Differential diagnosis of common causes of vomiting in childhood include:

• Possetting, i.e. effortless recurrent regurgitation of gastric contents, reflects developmental immaturity of cardiac sphincter in early infancy to prevent backflow of gastric contents. Babies often outgrow it by 7-8 months and no intervention is required except burping after each feed.

• Esophageal obstruction (foreign body or strictures) presents with vomiting soon after feeding and contains recently ingested undigested food. Liquid are better tolerated than semi-solids.

• GERD: Vomiting is more common in lying down position and semisolids are better tolerated than liquids (Ch 14.6.2).

• Food poisoning often involves other members of family/group and diarrhea is common.

• Infantile hypertrophic pyloric stenosis (IHPS) is associated with typically projectile and non-bilious vomiting after 15-20 minutes of feeds, along with a mass, which is visible after feeds and disappears after vomiting (Ch 14.8.1).

• Cyclic vomiting refers to stereotypic episodes of intense nausea and vomiting with normal intervening period (see below).

• Intestinal obstruction: Vomiting is usually bilious, associated with abdominal distension and constipation. (Ch 14.13)

• Raised ICP in neurological disorders leads to early morning projectile vomiting, associated with headache, which is relieved after vomiting. Paroxys­mal vomiting with preceding headache indicates migraine.

• Rumination denotes recurrent regurgitation of recently ingested food with subsequent spitting/ remastication and swallowing. Self-induced vomiting is seen in adolescent girls with anorexia nervosa or bulimia.

Management of vomiting includes:

• Symptomatic antiemetic therapy, preferably with Dom­peridone (PO 0.3 mg/kg/dose) or Ondansetron (PO/ IV 0.15-0.3 mg/kg/dose).

Antiemetic drugs act by suppression of CTZ or facilitation of gastric emptying and include- (a) Dopamine antagonists, e.g. metoclopramide or domperidone; or (b) Serotonin-3 antagonists, e.g. ondansetron or granisetron. Other antiemetics, e.g. CTZ suppressors (prochlorperazine) or Antihistamines, (promethazine) are not used in children due to high risk of extrapyramidal reactions and sedation respectively.

• Correction of fluid and electrolyte imbalance.

• Evaluation of primary cause and its treatment.

Cyclic vomiting: Most cases have onset in pre-school or school age (gt; 2 years of age) and family history is present in 30-40%. Exact cause is unknown but each episode usually begins with autonomic features, e.g. lethargy, tachycardia, hypertension and abdominal pain.

Diagnostic criteria includes: (a) minimum total 5 epi­sodes or 3 episodes in 6 months, (b) each episode lasting from 1 hour to 10 days with at least one week normal interval, (c) gt; 4 vomiting/hour for at least one hour, and

(c) no identifiable cause.

Management includes antiemetics and supportive therapy during the episode, which can be prevented with Cyproheptadine (PO.25-0.5 mg/kg/d q8-12hr) or Propranolol (Po 0.25-1 mg/kg/d at bed time.

14.4.3