The most likely causative organism for the symptoms of this child is Giardia lamblia.Giardiasis results in fat malabsorption thus giving rise to greasy stools. It is resistant to chlorination, hence has a risk of transfer in swimming pools.World Health Organisation definitions- Diarrhoea: > 3 loose or watery stool per day- Acute diarrhoea < 14 days- Chronic diarrhoea > 14 daysConditions that usually present as acute diarrhoea:- Gastroenteritis: It may be accompanied by abdominal pain or nausea/vomiting.- Antibiotic therapy: Can occur following antibiotic therapy, especially common with broad spectrum antibiotics.Conditions that usually present as chronic diarrhoea:- Irritable bowel syndrome: It is a very common disease.The most consistent features are abdominal pain, bloating and change in bowel habit. Patients may be divided into those with diarrhoea predominant IBS and those with constipation-predominant IBS.Features such as lethargy, nausea, backache and bladder symptoms may also be present in these patients.- Ulcerative colitis: It presents as bloody diarrhoea. Patients can also present with crampy abdominal pain and weight loss. Faecal urgency and tenesmus may be seen.- Crohn’s disease: It is also associated with crampy abdominal pains and diarrhoea. Bloody diarrhoea less common than in ulcerative colitis. Other features include malabsorption, mouth ulcers perianal disease and intestinal obstruction – Colorectal cancer: It is very rare in children. The symptoms depend on the site of the lesion but include diarrhoea, rectal bleeding, anaemia and constitutional symptoms like weight loss and anorexia.- Coeliac disease: In children, it may present with failure to thrive, diarrhoea and abdominal distension.Other conditions associated with diarrhoea include thyrotoxicosis, laxative abuse, appendicitis, and radiation enteritis.

The Green Book guidelines report in an active infection (HBeAg+ and HBsAg+) to give the vaccine as well as immunoglobulin. If antibodies are present it is not active infection (anti-Hbe) and then in that case only the vaccine, and no immunoglobulin, would be given. The presence of HBeAg means a person is infectious and can transmit to other people.

Projectile vomiting is the hallmark symptom of hypertrophic pyloric stenosis. It is the most common cause of intestinal obstruction in infancy, which has a male-to-female predominance of 4-5:1. Current management recommendations include ultrasonography for diagnosis, correction of electrolytes, and surgical intervention.

Total parenteral nutrition (TPN) frequently causes derangement of liver function in children. Other options:- While line sepsis and thromboembolism are recognised complications of TPN, they do not occur frequently. – A child who is on TPN will require regular blood tests because of the potential for the development of electrolyte abnormalities. Need to observe their liver function, in order to provide TPN more accurately.

The coeliac axis supplies the liver and stomach and from the oesophagus to the first half of the duodenum. The second half of the duodenum to the first two thirds of the transverse colon is supplied by the superior mesenteric artery. The inferior mesenteric supplies the last third of the transverse colon (approximately from the splenic flexure) to the first third of the rectum. The last two thirds of the rectum are supplied by the middle rectal artery. The greater curvature of the stomach is supplied by branches of the splenic artery, which itself comes from the coeliac axis.

Gastroesophageal reflux occurs in almost all infants, manifesting as wet burps after feeding. The spit-ups appear effortless and not particularly forceful.Infants in whom reflux has caused GERD have additional symptoms, such as irritability, feeding refusal, and/or respiratory symptoms such as chronic recurrent coughing or wheezing and sometimes stridor. Much less commonly, infants have intermittent apnoea or episodes of arching the back and turning the head to one side (Sandifer syndrome). Infants may fail to gain weight appropriately or, less often, lose weight.Incidence of gastroesophageal reflux increases between 2 months and 6 months of age (likely due to an increased volume of liquid at each feeding) and then starts to decrease after 7 months. Gastroesophageal reflux resolves in about 85% of infants by 12 months and in 95% by 18 months.

Intussusception is the most suggested case here based on the child’s symptoms. The urgent course of treatment is to bring the child to a paediatric surgical unit. If air reduction attempts fail, surgery will have to be done. Risk factors for intussusception include viral infection and intestinal lymphadenopathy.

Bulimia nervosa is an eating disorder that involves frequent episodes of binge eating followed by inappropriate purging behaviour. The underlying reason for this behaviour is distorted self-image. Bulimia leads to several medical issues, including various laboratory derangements. Among these deranged laboratory parameters are the hormone cholecystokinin, which is found to be decreased in women having bulimia. It is hypothesized that the bingeing episodes observed in patients with bulimia are due to lower levels of CCK since normal levels of CCK are involved in maintaining satiety and controlling the urge to binge eat.

The most probable diagnosis for this patient would be congenital hypertrophic pyloric stenosis.Congenital Hypertrophic Pyloric Stenosis (CHPS):Pyloric stenosis should be ruled out in any baby who presents with a long-term history of vomiting and failure to thrive. Infants typically present with projectile, non-bilious vomiting and are said to be hungry and wanting to feed despite poor weight gain. A blood gas would be helpful in this instance, although the diagnosis can be made more accurately by observing the stenosis during ultrasound. Many infants have symptoms of gastroesophageal reflux disease, although only a small minority are unable to gain weight adequately. A UTI in infants can present with non-specific symptoms, but they might have a fever and can show poor feeding. Malrotation will present with bilious vomiting.The definitive surgical management is the Ramsteadt’s pyloromyotomy.

Laxatives have been shown to be beneficial in the treatment of chronic childhood constipation. Studies have shown that polyethylene glycol, mineral oil, magnesium hydroxide, and lactulose are effective and can be used for a prolonged periods without risk.

Most experts suggest that parents reassurance in case of infantile gastro-oesophageal reflux (GOR) is a sufficient initial measure that involves education about regurgitation and lifestyle changes.

Food poisoning is defined as an illness caused by the consumption of food or water contaminated with bacteria and/or their toxins, or with parasites, viruses, or chemicals. The most common pathogens are Norovirus, Escherichia coli, Salmonella, Clostridium perfringens, Campylobacter, and Staphylococcus aureus.The following are some of the salient features of food poisoning:Acute diarrhoea in food poisoning usually lasts less than 2 weeks. Diarrhoea lasting 2-4 weeks is classified as persistent. Chronic diarrhoea is defined by duration of more than 4 weeks.The presence of fever suggests an invasive disease. However, sometimes fever and diarrhoea may result from infection outside the GI tract, as in malaria.A stool with blood or mucus indicates invasion of the intestinal or colonic mucosa.Reactive arthritis can be seen with Salmonella, Shigella, Campylobacter, and Yersinia infections.A profuse rice-water stool suggests cholera or a similar process.Abdominal pain is most severe in inflammatory processes. Painful abdominal cramps suggest underlying electrolyte loss, as in severe cholera.A history of bloating should raise the suspicion of giardiasis.Yersinia enterocolitis may mimic the symptoms of appendicitis.Proctitis syndrome, seen with shigellosis, is characterized by frequent painful bowel movements containing blood, pus, and mucus. Tenesmus and rectal discomfort are prominent features.Consumption of undercooked meat/poultry is suspicious for Salmonella, Campylobacter, Shiga toxin E coli, and C perfringens.Consumption of raw seafood is suspicious for Norwalk-like virus, Vibrioorganism, or hepatitis A.Consumption of homemade canned foods is associated with C botulinum.Consumption of unpasteurized soft cheeses is associated with Listeria, Salmonella, Campylobacter, Shiga toxin E coli, and Yersinia.Consumption of deli meats notoriously is responsible for listeriosis.Consumption of unpasteurized milk or juice is suspicious for Campylobacter, Salmonella, Shiga toxin E coli, and Yersinia.Salmonella has been associated with consumption of raw eggs.