Observational studies fall under the category of analytic study designs and are further sub-classified as observational or experimental study designs. The goal of analytic studies is to identify and evaluate causes or risk factors of diseases or health-related events. The differentiating characteristic between observational and experimental study designs is that in the latter, the presence or absence of undergoing an intervention defines the groups. By contrast, in an observational study, the investigator does not intervene and rather simply “observes” and assesses the strength of the relationship between an exposure and disease variable.Three types of observational studies include cohort studies, case-control studies, and cross-sectional studies. Case-control and cohort studies offer specific advantages by measuring disease occurrence and its association with an exposure by offering a temporal dimension (i.e. prospective or retrospective study design). Cross-sectional studies, also known as prevalence studies, examine the data on disease and exposure at one particular time point. Because the temporal relationship between disease occurrence and exposure cannot be established, cross-sectional studies cannot assess the cause and effect relationshipDisadvantage of Cohort study is Susceptible to selection bias.

Cot death also know as SIDS or Sudden Infant Death syndrome. Putting a baby to sleep on his back has been shown to reduce the risk of SIDS.

The most appropriate step in this patient would be to admit the patient for enteral rehydration via a nasogastric tube.Enteral rehydration:Oral rehydration is the most preferred way of rehydrating children. If a child is not tolerating small-frequent-feeds, then nasogastric rehydration is an underused next best step. The fluid can be run through a continuous pump so that it is better tolerated. Note:Intravenous fluids are effective but can have profound effects on the serum electrolyte balance if not monitored closely. Most children will tolerate fluids in an emergency department, but failure to take fluids orally is not an indication for intravenous therapy.

Urine culture confirms a diagnosis of a UTI. A kidney ultrasound will be the next best investigation because it will help us to visualise the bladder, kidneys, and ureters to rule out any congenital obstruction in the urinary tract that might be the actual cause of infection in this 2-month old girl.

Cranial nerve VI, also known as the abducent nerve, innervates the ipsilateral lateral rectus (LR), which functions to abduct the ipsilateral eye. Patients usually present with an isolated abduction deficit, binocular horizontal diplopia, worse in the distance, and esotropia in primary gaze. Patients also may present with a head-turn to maintain binocularity and binocular fusion and to minimize diplopiaExamination for a sixth nerve palsy involves documenting the presence or absence of papilledema, examining the ocular motility, evaluating the eyelids and pupils, and excluding involvement of other cranial nerves (e.g., V, VII, VIII).

Precocious puberty is the development of secondary sexual characteristics before the age of 8 in females, and 9 in males. The first sign of early puberty in females is breast enlargement, followed by the appearance of pubic and axillary hair, and finally menarche, 2-3 years after the onset of thelarche. Precocious puberty is caused by the premature activation of the hypothalamic-pituitary-gonadal axis where FSH and LH levels are raised. Less common is the gonadotrophin independent form, which is due to excess sex hormones, but low FSH and LH levels.

Renal stones < 5mm generally pass spontaneously with adequate fluid intake. Stones 5mm-10mm with pain not resolving, require medical expulsive therapy with Nifedipine or Tamsulosin. For stones larger than 10mm, ESWL or Ureteroscopy is indicated. For stones as big as 2cm, percutaneous nephrolithotomy should be applied.

The patient is most likely to have Bulimia nervosa. A young girl with a low body mass contributes to the low urea. Hypokalaemia and hyponatraemia are due to vomiting. Her urine sodium is also low.- In Addison’s diseases, there are low levels of sodium and high levels of potassium in the blood. In acute adrenal crisis: The most consistent finding is elevated blood urea nitrogen (BUN) and creatinine. Urinary and sweat sodium also may be elevated. – In Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) there is hyponatremia with corresponding hypo-osmolality, continued renal excretion of sodium, urine less than maximally dilute and absence of clinical evidence of volume depletion.

By 15 months, it’s common for many toddlers to:- say three to five words.- understand and follow simple commands.- point to one body part.- walk alone and begin to run.- climb on furniture.- make marks with a crayon.- imitate activities, such as housework.

The most probable diagnosis for this patient would be a duplex kidney with an ectopic ureter inserting below the bladder neck. Rationale: The Weigert-Myer law states that the upper moiety ureter inserts inferior and medial to the lower moiety ureter. Other options:- Horseshoe kidney would display as a single pelvic kidney on an ultrasound scan.- Ureterocele would be a cystic lesion within the bladder or may prolapse at birth. – Continence should not be affected by polycystic kidney disease. – The overactive bladder would cause frequency and urgency, neither of which is mentioned in the history.

Successful administration of median nerve block can be confirmed by the inability to abduct the thumb. The median nerve supplies all the muscles in the anterior compartment of the forearm, apart from the flexor carpi ulnaris and the flexor digitorum profundus to the outer two fingers: so these two fingers can still be flexed. There is a sensory loss to the thumb, index, middle and half of the ring fingers. Absence of thumb abduction due to paralysis of abductor pollicis brevis is a good test for median nerve paralysis.Other options:- The radial nerve supplies the extensors – hence wrist drop does not occur in this scenario. – The ulnar nerve supplies the skin of the ulnar side of the hand. Hence anaesthesia will not affect this area. – The ulnar nerve also supplies the interossei muscles of the hand, which affect abduction and adduction of the fingers.

Infants may require tracheal intubation if:- direct tracheal suctioning is required- effective bag-mask ventilation cannot be provided- chest compressions are performed- endotracheal (ET) administration of medications is desired- congenital diaphragmatic hernia is suspected, or – a prolonged need for assisted ventilation exists.

Cricothyroidectomy is done in life threatening condition, where an incision is made in cricothyroid membrane to establish a patent airway.

Human breast milk composition changes with the progressive age of the infant. Breastmilk produced for a preterm baby often has a higher caloric content than breastmilk for a term baby. After the production of colostrum in the first days of life, the milk continues to mature. by week 4-6 milk can be considered fully mature. The average calories found in mature breastmilk are about 70kcal/100ml

Torsade de pointes is an uncommon and distinctive form of polymorphic ventricular tachycardia (VT) characterized by a gradual change in the amplitude and twisting of the QRS complexes around the isoelectric line.Conditions associated with torsade include the following:Electrolyte abnormalities – Hypokalaemia, hypomagnesemia, hypocalcaemiaEndocrine disorders – Hypothyroidism, hyperparathyroidism, pheochromocytoma, hyperaldosteronism, hypoglycaemiaCardiac conditions – Myocardial ischemia, myocardial infarction, myocarditis, bradyarrhythmia, complete atrioventricular (AV) block, takotsubo cardiomyopathyIntracranial disorders – Subarachnoid haemorrhage, thalamic hematoma, cerebrovascular accident, encephalitis, head injuryNutritional disorders – Anorexia nervosa, starvation, liquid protein diets, gastroplasty and ileojejunal bypass, celiac diseaseRisk factors for torsade include the following:Congenital long QT syndromeFemale genderAcquired long QT syndrome (causes of which include medications and electrolyte disorders such as hypokalaemia and hypomagnesemia)BradycardiaBaseline electrocardiographic abnormalitiesRenal or liver failure

Based on the presentation, the child most probably is suffering from a refractive error.Astigmatism, myopia and high hypermetropia could all cause these symptoms. This child has difficulty in using vision for finer tasks such as reading. Mild to moderate refractive error would not impair the child’s ability to play or even watch television as for the child in question. Note: Refractive error is the most common treatable cause of reduced vision in children all over the world! Other options:- A congenital cataract is rare and retinal dystrophy is even rarer. – Amblyopia would suggest poor vision in only one eye, something that might not cause symptoms in this age group. – Parents or teachers would have probably noticed squint if it was present.

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.

Normal QT interval in a 6 months old baby is < 0.44 seconds. A duration exceeding this value is referred to as QT interval prolongation, which is associated with some important congenital syndromes that include Brugada syndrome which is characterized by vasovagal syncope and sudden cardiac death, Jervell and Lange-Nielsen syndrome which is associated with congenital deafness, Andersen syndrome which is marked by bone deformities, and Timothy syndrome with associated heart disease and immunodeficiency. Romano-Ward syndrome is the commonest cause of congenital QT prolongation with no associated extra-cardiac manifestations. Lown-Ganong-Levine syndrome is characterized by a shortened PR interval and a normal QRS duration.

The most appropriate action in this baby would be to perform HIV PCR and commence cART and PCP prophylaxis if HIV positive.Treatment guidelines for HIV-positive infants state that all should receive combination antiretroviral therapy (cART) and Pneumocystis jiroveci pneumonia (PJP) prophylaxis, irrespective of CD4 count or viral load.

Congenital LQTS arises from mutations in genes that code for ion channels within myocytes.These mutations all cause ventricular action potentials to be prolonged, resulting in a lengthened QT interval on ECG. The congenital long-QT syndrome (LQTS) is a life-threatening cardiac arrhythmia syndrome that represents a leading cause of sudden death in the young. LQTS is typically characterized by a prolongation of the QT interval on the ECG and by the occurrence of syncope or cardiac arrest, mainly precipitated by emotional or physical stress.LQTS type 1Most common type of congenital LQTSDefect: loss of function mutation on the KCNQ1 gene located on chromosome 11p → defective slow delayed rectifier voltage-gated potassium channelSubtypesJervell and Lange-Nielsen syndrome Associated with congenital deafnessAutosomal recessiveAssociated with ventricular tachyarrhythmiasRomano-Ward syndrome No associated deafnessAutosomal dominantAssociated with ventricular tachyarrhythmias

Based on the clinical scenario, the most likely risk factor in this child to develop gallstones is sickle cell disease.Note:Haemolysis is the most frequent cause for gallstones in children and the likeliest cause because of his ethnicity would be sickle cell disease. The gallstones are pigmented which form from bilirubin. 70% of patients with sickle cell disease will develop gallstones| the prevalence of gallstones is related to the rate of haemolysis.Other options:- Gilbert’s syndrome: it is a common condition in which bilirubin glucuronidation (i.e. converting bilirubin into a water-soluble form) is affected. During times of stress (viral illness, fasting, etc.) there is an excess bilirubin production, and jaundice may develop. It is a benign condition but there is some evidence of an increased risk of developing gallstones. However, sickle cell disease is a more likely risk factor in this case.- Hereditary spherocytosis: Hereditary spherocytosis is a disease of the white population and is less likely to be the underlying cause in this case.- Male gender: After puberty, the incidence of gallstones is higher in women. Before puberty, the incidence is equal.- Obesity: Obesity is a risk factor for gallstones and is thought to be behind the rising incidence among young adults. Nevertheless, haemolytic states remain the most common reason for gallstones in children.

Endometriosis is defined as the presence of normal endometrial mucosa (glands and stroma) abnormally implanted in locations other than the uterine cavityAbout one third of women with endometriosis remain asymptomatic. When they do occur, symptoms, such as the following, typically reflect the area of involvement:- Dysmenorrhea- Heavy or irregular bleeding- Pelvic pain- Lower abdominal or back pain – Dyspareunia- Dyschezia (pain on defecation) – Often with cycles of diarrhoea and constipation- Bloating, nausea, and vomiting- Inguinal pain- Pain on micturition and/or urinary frequency- Pain during exercise- Patients with endometriosis do not frequently have any physical examination findings beyond tenderness related to the site of involvement. – The most common finding is nonspecific pelvic tenderness.

Congenital adrenal hyperplasia is a common cause of virilisation in females that can present as ambiguous genitalia at birth. Deficiency of the 21-alphahydroxylase enzyme is implicated in excess mineralocorticoid and androgens produced by the adrenal gland. Virilisation occurs when excess androgens are converted to testosterone in a genetically female foetus, causing the genitalia to resemble male genitalia. A deficiency of 5-alpha hydroxylase would rather decrease the production of testosterone and lead to the presentation of external female genitalia in a genetically male foetus. Autoantibodies against glutamic acid are seen in type 1 diabetes mellitus, while defects in the AIRE gene and the FOXP3 affect components of the immune system.

Hydrops fetalis is a serious condition characterized by excessive fluid accumulation resulting in oedema in one or more of the fetal compartments. The most likely cause is fetal anaemia, and the condition may lead to ascites and pleural effusion. The anaemia that results in hydrops may be caused by Rh incompatibility, Parvovirus B19 infection, toxoplasmosis, hepatitis B, maternal syphilis (strong association), Cytomegalovirus, Turner syndrome, and Noonan syndrome.

Maternal and fetal toxoplasma infection may be avoided by advising pregnant women to wear gloves when gardening or handling cat litter and to cook meat thoroughly. Affected babies are treated with pyrimethamine, sulfadiazine, and folic acid.

The percentages of body water contained in various fluid compartments add up to total body water (TBW). This water makes up a significant fraction of the human body, both by weight and by volume. Ensuring the right amount of body water is part of fluid balance, an aspect of homeostasis. The extracellular fluid (ECF) includes all fluids outside the cells. This fluid can be divided into three fluid departments: interstitial (in the tissue spaces) fluid, blood plasma and lymph, and specialised compartments called transcellular fluid. The extracellular fluid surrounds all the cells in the body and is in equilibrium with the intracellular fluid. So, its composition must remain fairly constant even though substances are passing into and out of the cells. The interstitial fluid, though called a fluid, is in a reality a gel-like composition made up of: water, proteoglycan molecules and collagen. The extracellular fluid constitutes 40% of total body water, with intracellular fluid making up the remaining 60%. It is relatively rich in glucose.

Epiglottitis is characterized by the abrupt onset of severe symptoms. Without airway control and medical management, symptoms may rapidly progress to respiratory obstruction and death in a matter of hours.Usually, no prodromal symptoms occur in children. Fever is usually the first symptom, and temperatures often reach 40°C. Acute epiglottitis may result in sudden, complete upper airway obstruction. Classic signs in children are four D’s: drooling, dyspnoea, dysphagia, and dysphonia.

Polycythaemia is a commonly occurring neonatal disorder, which is characterized by a venous haematocrit ≥ 65%. It increases the blood viscosity and causes microcirculatory flow impairment in the end-organs. Causes of polycythaemia are multi-factorial, but the significant risk factors are maternal diabetes, SGA, LGA or post-term birth, infants with chromosomal abnormalities, and delayed clamping of the cord. Jaundice is not a recognized risk factor for polycythaemia.

Based on the clinical scenario, the most probable diagnosis is acute appendicitis.Acute appendicitis presents typically with central abdominal pain migrating to the right iliac fossa, anorexia, nausea and fever. The temperature usually does not go beyond 40C. Although appendicitis is a clinical diagnosis, an ultrasound scan showing an appendix width of greater than 6mm is diagnostic.Pyrexia, guarding, and pain are all in keeping with appendicitis.Other options:- Cholecystitis is very rare in children, and although gall stones are present, there is no jaundice or biliary tree dilatation suggested by the scan.- Impacted Gall Stone: There is no mention of common bile duct dilatation in the clinical scenario.- Sickle Cell Crisis: A sickle cell crisis should not cause guarding, or an ultrasound scan finding of a dilated appendix base.- Gastroenteritis: Gastroenteritis would not produce the ultrasound scan findings described above with a thickened appendix.

The boy is most likely to have sustained an injury to his brachial plexus as a result of upward traction of his arm for an extended period of time. We can rule out the topmost nerve roots of the brachial plexus, C6 and C7 as these supply the larger muscles of the arm responsible for moving the shoulder, the elbow and the wrist. The anatomical structure affected is therefore the T1 nerve root which is responsible for movement of the muscles in the hand. This type of injury is called a Klumpke’s Palsy, which is the result of a hyper-abducted trauma to the arm, damaging the C8 and T1 nerve roots. While the radial and ulnar nerve also innervate the hand, the history given points to Klumpke’s palsy as the best explanation for this mechanism of injury.