Dead space refers to inhaled air that does not take part in gas exchange. Because of this dead space, taking deep breaths slowly is more effective for gas exchange than taking quick, shallow breaths where a large proportion is dead space. Use of a snorkel by a diver increases the dead space marginally. Anatomical dead space refers to the gas in conducting areas such as mouth and trachea, and is roughly 150 ml (2.2 ml/kg body weight). This corresponds to a third of the tidal volume (400-500 ml). It can be measured by Fowler’s method, a nitrogen wash-out technique. It is posture-dependent and increases with increase in tidal volume. Physiological dead space is equal to the anatomical dead space plus the alveolar dead space, where alveolar dead space is the area in the alveoli where no effective exchange takes place due to poor blood flow in capillaries. This physiological dead space is very small normally (< 5 ml) but can increase in lung diseases. Physiological dead space can be measured by Bohr’s method. Total ventilation per minute (minute ventilation) is given by the product of tidal volume and the breathing rate. Here, the total ventilation is 600 ml times 12 breaths/min = 7200 ml/min. The problem mentions alveolar ventilation to be 6000 ml/min. Thus, the difference between the alveolar ventilation and total ventilation is 7200 – 6000 ml/min = 1200 ml/min, or 100 ml per breath at 12 breaths per min. This 100 ml is the dead space volume.

Proctalgia fugax (PF) is a benign painful rectal condition that is defined as intermittent, recurring, and self-limiting pain in the anorectal region in the absence of organic pathology. The pain of proctalgia fugax is sharp or gripping and severe. Similar to other urogenital focal pain syndromes, such as vulvodynia and proctodynia, the causes remain obscure. Stress and sitting for prolonged periods often increase the frequency and intensity of attacks of proctalgia fugax. Patients often feel an urge to defecate with the onset of the paroxysms of pain . Depression often accompanies the pain of proctalgia fugax but is not thought to be the primary cause. The symptoms of proctalgia fugax can be so severe as to limit the patient’s ability to perform activities of daily living. Reassurance has proven to help in many cases as the condition has been linked to stress.

Surgical resection is the principal therapy for gastric cancer, as it offers the only potential for cure. A subtotal gastrectomy is usually performed for tumours of the distal stomach. Subtotal gastrectomy is the treatment of choice for middle and distal-third gastric cancer as it provides similar survival rates and better functional outcome compared to total gastrectomy, especially in early-stage disease with favourable prognosis. D2 dissections are recommended by the National Comprehensive Cancer Network over D1 dissections. A pancreas-and spleen-preserving D2 lymphadenectomy is suggested, as it provides greater staging information, and may provide a survival benefit while avoiding its excess morbidity when possible. Patients that undergo D2 lymphadenectomy as a standard part of surgical resection of gastric adenocarcinoma generally have better stage-for-stage overall survival figures compared to patients undergoing less extensive lymphadenectomies.
After partial gastrectomy, some patients report disorders such as reflux esophagitis and alkaline gastritis, as well as dumping syndrome, delayed gastric emptying and malabsorption, which are defined as functional dyspepsia. Duodenogastric reflux is recognized to be a major cause of clinical symptoms after resection.
Roux-Y reconstruction seems to be effective in reducing bile reflux into the stomach, compared to Billroth I and II procedure, and conversion to this procedure has been reported in patients with symptomatic uncontrolled reflux disease.

The patient has Haemorrhoid Disease
A total of 40% of individuals with haemorrhoids are asymptomatic.
For internal haemorrhoids, bleeding is the most commonly reported symptom. The occurrence of bleeding is usually associated with defecation and almost always painless. The blood is bright red and coats the stool at the end of defection.
Another frequent symptom is the sensation of tissue prolapse. Prolapsed internal haemorrhoids may accompany mild faecal incontinence, mucus discharge, a sensation of perianal fullness, and irritation of perianal skin. Pain is significantly less common with internal haemorrhoids than with external haemorrhoids but can occur in the setting of prolapsed, strangulated internal haemorrhoids that develop gangrenous changes due to the associated ischemia.
In contrast, external haemorrhoids are more likely to be associated with pain, due to activation of perianal innervations associated with thrombosis. Patients typically describe a painful perianal mass that is tender to palpation. This painful mass may be initially increasing in size and severity over time. Bleeding can also occur if ulceration develops from necrosis of the thrombosed haemorrhoid, and this blood tends to be darker and more clotted than the bleeding from the internal disease. Painless external skin tags often result from previous oedematous or thrombosed external haemorrhoids.

Lifestyle and dietary modification are the mainstays of conservative medical treatment of haemorrhoid disease. Specifically, lifestyle modifications should include increasing oral fluid intake, reducing fat consumptions, avoiding straining, and regular exercise. Diet recommendations should include increasing fibre intake, which decreases the shearing action of passing a hard stool.
Most patients with grade I and II and select patients with grade III internal hemorrhoidal disease who fail medical treatment can be effectively treated with office-based procedures.
For internal haemorrhoids, rubber band ligation, sclerotherapy, and infrared coagulation are the most common procedures but there is no consensus on optimal treatment. Overall, the goals of each procedure are to decrease vascularity, reduce redundant tissue, and increase hemorrhoidal rectal wall fixation to minimize prolapse.
Rubber band ligation is the most commonly performed procedure in the office and is indicated for grade II and III internal haemorrhoids.

The diaphragm and external intercostals are muscles of inspiration as they increase the volume of thoracic cavity and reduce the intrathoracic pressure. Muscles of expiration include abdominal muscles and internal intercostals.

Kupffer cells found in the liver are part of the monocyte-reticular system. They are specialised macrophages and primarily function to recycle old and damaged RBCs. The RBCs are phagocytosed and the haemoglobin is broken down into haem and globin. The haem is further broken down into iron that is recycled and bilirubin that is conjugated with glucuronic acid and excreted in the bile.

Spermatocele, also known as a spermatic cyst is a cystic mass usually occurring at the upper pole of the testis. Differential diagnosis included hydrocele as both are cystic, painless and transilluminant. Ultrasound is a useful modality. If symptomatic or large, surgical excision can be done.

Pyloric stenosis is a narrowing of the opening from the stomach to the first part of the small intestine (the pylorus). Symptoms include projectile vomiting without the presence of bile. This most often occurs after the baby is fed. The typical age that symptoms become obvious is two to twelve weeks old.

The cause of pyloric stenosis is unclear. Risk factors in babies include birth by caesarean section, preterm birth, bottle feeding, and being first born. The diagnosis may be made by feeling an olive-shaped mass in the baby’s abdomen. This is often confirmed with ultrasound. It is four times more likely to occur in males, and is also more common in the first born. Rarely, infantile pyloric stenosis can occur as an autosomal dominant condition.

It is uncertain whether it is a congenital anatomic narrowing or a functional hypertrophy of the pyloric sphincter muscle.
Babies with this condition usually present any time in the first weeks to months of life with progressively worsening vomiting. The vomiting is often described as non-bile stained (non bilious) and projectile vomiting, because it is more forceful than the usual spitting up (gastroesophageal reflux) seen at this age. Some infants present with poor feeding and weight loss but others demonstrate normal weight gain. Dehydration may occur which causes a baby to cry without having tears and to produce less wet or dirty diapers due to not urinating for hours or for a few days. Symptoms usually begin between 3 to 12 weeks of age. Findings include epigastric fullness with visible peristalsis in the upper abdomen from the person’s left to right. Constant hunger, belching, and colic are other possible signs that the baby is unable to eat properly.

The American Society of Colon and Rectal Surgeons (ASCRS) states that clinicians should typically offer haemorrhoidectomy to patients with symptomatic disease from external haemorrhoids or combined internal/external haemorrhoids with prolapse. For those who undergo surgical haemorrhoidectomy, a multimodality pain regimen is recommended to reduce use of narcotics and promote a faster recovery.

Arachidonic acid is normally present in the phospholipids that make up the cell membrane and is cleaved by phospholipase A2 from the phospholipid. Arachidonic acid is a precursor for the production of eicosanoids which include: 1) prostaglandins, prostacyclins and thromboxane, 2) leukotrienes and 3) anandamides. The production of these products along with their action on the body is called the arachidonic acid cascade.

Glomerular filtration rate (GFR) is the volume of fluid filtered from the renal (kidney) glomerular capillaries into the Bowman’s capsule per unit time. GFR is equal to the inulin clearance because inulin is freely filtered into Bowman’s capsule but is not reabsorbed or secreted. The clearance (C) of any substance can be calculated as follows: C = (U × V)/P, where U and P are the urine and plasma concentrations of the substance, respectively and V is the urine flow rate. Thus, glomerular filtration rate = (1.0 × 2. 0)/0.01 = 200 ml/min.

Created by the small intestinal cells, chylomicrons are large lipoprotein molecules which transport lipids to the liver, adipose, cardiac and skeletal tissue. Chylomicrons are mainly composed of triglycerides (,85%) along with some cholesterol and cholesteryl esters. Apo B-48 is the main apolipoprotein content.

As per Fick’s principle, VO2 = (CO × CAO2) – (CO × CVO2) where VO2 = oxygen consumption, CO = cardiac output, CAO2 = oxygen concentration of arterial blood and CVO2 = oxygen concentration of venous blood. Thus, CO = VO2/CAO2– CVO2, CO = 500/0.24 – 0.16, CO = 500/0.8, CO = 6.25 l/min.

In adults, the most common primary site of tumour is in the lungs, compared to children wherein the most common primary site is the blood.

Answer: MAG 3 renogram

This is the agent of choice due to a high extraction rate, which may be necessary for an obstructed system. Diuretic (furosemide) renogram is performed to evaluate between obstructive vs. nonobstructive hydronephrosis. The non-obstructive hydronephrosis will demonstrate excretion (downward slope on renogram) after administration of diuretic from the collecting system. Whereas mechanical obstructive hydronephrosis will show no downward slope on renogram, with retained tracer in the collecting system.

Pelviureteric junction (PUJ) obstruction/stenosis can be one of the causes of an obstructive uropathy. It can be congenital or acquired with a congenital PUJ obstruction being one of the most common causes of antenatal hydronephrosis. This is defined as an obstruction of the flow of urine from the renal pelvis to the proximal ureter.
Many cases are asymptomatic and identified incidentally when the renal tract is imaged for other reasons. When symptomatic, symptoms include recurrent urinary tract infections, stone formation and even a palpable flank mass. They are also at high risk of renal injury even by minor trauma.

Symptom: Classically intermittent pain after drinking large volumes of fluid or fluids with a diuretic effect is described, due to the reduced outflow from the renal pelvis into the ureter.

Tc-99m DMSA (dimercaptosuccinic acid) is a technetium radiopharmaceutical used in renal imaging to evaluate renal structure and morphology, particularly in paediatric imaging for detection of scarring and pyelonephritis. DMSA is an ideal agent for the assessment of renal cortex as it binds to the sulfhydryl groups in proximal tubules at the renal cortex with longer retention than other agents. This results in higher concentration and hence much higher resolution with pinhole SPECT imaging. Also, it allows better assessment of differential renal function. It is a static scan as opposed to dynamic DTPA or MAG3 scans.

Hyperphosphatemia is an electrolyte disturbance in which there is an abnormally elevated level of phosphate in the blood. It is caused by conditions that impair renal phosphate excretion (ex: renal insufficiency, hypoparathyroidism, parathyroid suppression) and conditions with massive extracellular fluid phosphate loads (ex: rapid administration of exogenous phosphate, extensive cellular injury or necrosis, transcellular phosphate shifts).

Fluconazole is a triazole antifungal drug used in the treatment and prevention of superficial and systemic fungal infections. Like other imidazole- and triazole-class antifungals, fluconazole inhibits the fungal cytochrome P450 enzyme, 14-demethylase. It is used to treat candidiasis, blastomycosis, coccidioidomycosis, cryptococcosis, histoplasmosis, dermatophytosis, and pityriasis versicolor.

Metaplasia is the transformation of one type of epithelium into another as a means to better cope with external stress on that epithelium. In this case metaplasia occurs due to the inflammation resulting from gastro-oesophageal reflux disease. Dysplasia is disordered cellular growth. Hyperplasia is an increase in cell number but not cell type i.e. transformation. Carcinoma is characterized by cellular atypia. Ischaemia would result in necrosis with ulceration. Carcinoma insitu involves dysplastic atypical cells with the basement membrane intact and atrophy would mean a decrease in number of cells.

Bile salts are formed out of cholesterol in the liver cells. Occasionally, precipitation of cholesterol occurs resulting into cholesterol stones developing in the gall bladder.
These cholesterol gallstones are the most common type and account for 80% of all gallstones. Another type, accounting for 20% gallstones is pigment stones which are composed of bilirubin and calcium salts. Occasionally, stones of mixed origin are also seen.

Warfarin-induced skin necrosis is a rare complication of anticoagulant therapy that requires immediate drug cessation. The most common cutaneous findings include petechiae that progress to ecchymoses and haemorrhagic bullae. Warfarin inactivates vitamin K-dependent clotting factors II, VII, IX, and X and vitamin K-dependent proteins C and S. The concentration of protein C falls more rapidly than other vitamin K-dependent factors because they have a shorter half-lives. Skin necrosis is seen mainly in patients with prior protein C deficiency.

The patient is in hypovolemic shock, he is transfused with blood to replace the volume lost. It is important not only to replace fluids but stop active bleeding in resuscitation. Fluid replacement will result in a decreased sympathetic discharge and adequate ventricular filling thus reducing total peripheral resistance and increasing cardiac output and cardiac filling pressures.

Normal values for various parameters are as follows:
Systolic arterial blood pressure (SBP): 90–140 mmHg.
Diastolic arterial blood pressure: 60–90 mmHg.
Mean arterial blood pressure (MAP): SBP + (2 × DBP)/3 (normal range: 70-105 mmHg).
Right atrial pressure (RAP): 2–6 mmHg.
Systolic right ventricular pressure (RVSP): 15–25 mmHg.
Diastolic right ventricular pressure (RVDP): 0–8 mmHg.
Pulmonary artery pressure (PAP): Systolic (PASP) is 15-25 mmHg and Diastolic (PADP) is 8–15 mmHg.
Pulmonary artery wedge pressure (PAWP): 6–12 mmHg.
Left atrial pressure (LAP): 6–12 mmHg.
Thus, the given value indicates that the position of catheter tip is likely to be in the pulmonary artery.

Sialolithiasis (also termed salivary calculi, or salivary stones), is a condition where a calcified mass or sialolith forms within a salivary gland, usually in the duct of the submandibular gland (also termed Wharton’s duct).
Signs and symptoms are variable and depend largely upon whether the obstruction of the duct is complete or partial, and how much resultant pressure is created within the gland.
The development of infection in the gland also influences the signs and symptoms:
– Pain, which is intermittent, and may suddenly get worse before mealtimes, and then slowly get better (partial obstruction).
– Swelling of the gland, also usually intermittent, often suddenly appearing or increasing before mealtimes, and then slowly going down (partial obstruction).
– Tenderness of the involved gland.
– Palpable hard lump, if the stone is located near the end of the duct. If the stone is near the submandibular duct orifice, the lump may be felt under the tongue.
– Lack of saliva coming from the duct (total obstruction).
– Erythema (redness) of the floor of the mouth (infection).
– Pus discharging from the duct (infection).
– Cervical lymphadenitis (infection).
– Bad Breath.
– Rarely, when stones form in the minor salivary glands, there is usually only slight local swelling in the form of a small nodule and tenderness.

The development of oedema in nephrotic syndrome has traditionally been viewed as an underfill mechanism. According to this view, urinary loss of protein results in hypoalbuminemia and decreased plasma oncotic pressure. As a result, plasma water translocates out of the intravascular space and results in a decrease in intravascular volume. In response to the underfilled circulation, effector mechanisms are then activated that signal the kidney to secondarily retain salt and water. While an underfill mechanism may be responsible for oedema formation in a minority of patients, recent clinical and experimental findings would suggest that oedema formation in most nephrotic patients is the result of primary salt retention. Direct measurements of blood and plasma volume or measurement of neurohumoral markers that indirectly reflect effective circulatory volume are mostly consistent with either euvolemia or a volume expanded state. The ability to maintain plasma volume in the setting of a decreased plasma oncotic pressure is achieved by alterations in transcapillary exchange mechanisms known to occur in the setting of hypoalbuminemia that limit excessive capillary fluid filtration.

C3b is cleaved from C3 complement with the help of the enzyme C3- convertase. It binds to the cell surface of the offending substance and opsonizes it. This makes it easy for the phagocytes to detect and eliminate them.
IgM does not act as an opsonin but igG does.
Selectins aid leukocytes to bind to the endothelial surfaces.
C5a is a chemo-attractant and histamine a vasodilator.
NADPH oxidises offending substance after phagocytosis within the macrophage.

It has been well established that any delay in the resumption of normal oral diet after major surgery is associated with increased rates of infectious complications and delayed recovery. Early oral diet is safe 4 h after surgery in patients with a new non-diverted colorectal anastomosis. Some report that low residue diet, rather than a clear liquid diet, after colorectal surgery is associated with less nausea, faster return of bowel function, and a shorter hospital stay without increasing postoperative morbidity when administered in association with prevention of postoperative ileus. Spontaneous food intake rarely exceeds 1200–1500 kcal/day. To reach energy and protein requirements, additional oral nutritional supplements are useful.

Primary pulmonary tuberculosis is seen in patients exposed to Mycobacterium tuberculosis for the firs time. The main radiographic findings in primary pulmonary tuberculosis include homogeneous parenchymal consolidation typically in the lower and middle lobes, lymphadenopathy, miliary opacities and pleural effusion.

Oesophageal dysphagia occurs when there is a difficulty with the passage of solid or liquid material through the oesophagus, specifically the region between the upper and lower oesophageal sphincter. It results from either abnormal motility of this segment of the oesophagus or obstruction.
Common causes of dysphagia:
Gastro-oesophageal reflux—waterbrash, regurgitation, due to dysmotility or stricture
Achalasia—classically hold-up relieved by carbonated beverages
Motility disorders—may be associated with central chest pain, systemic disease (scleroderma, dermatomyositis)
Oesophageal cancer—progressive, weight loss
Head and neck cancer—pain, dysphagia, otalgia, >90% smokers, often excess alcohol consumption
Pharyngeal pouch—slowly progressive, regurgitation, gurgling
Web—able to swallow only small amounts, “can’t swallow tablets”
Stroke
Neurodegenerative disorders—parkinsonism, motor neurone disease, multiple sclerosis, myasthenia gravis
Presbyphagia

Endoscopy has the advantage of potentially yielding a histological diagnosis. The overall rate of oesophageal perforation after flexible endoscopy involving oesophageal instrumentation, biopsy, or dilatation is 2.6%

Oesophageal manometry remains the investigation of choice in suspected motility disorders. Manometry can classify oesophageal dysmotility into rare specific disorders such as achalasia and diffuse oesophageal spasm or more common non-specific motility disorders that do not respond directly to drug treatment but may improve if related reflux or psychiatric disturbances are treated. The symptoms of non-specific motility disorders may have an uncertain relation to the manometric abnormalities

Management is based on the history, findings of the clinical investigations, and prognosis for the individual patient. The underlying disorder is treated, but the impact of dysphagia on nutrition and hydration will compromise any intervention unless managed effectively. Poor physical condition from malnutrition or dehydration will lead to a suboptimal rehabilitation process, in both duration and completeness of recovery and inadequate management of dysphagia contributes to this. A malnourished person is at risk of decompensation of the swallow, leading to dysphagia. The clinical swallow assessment is used to determine safely modified diets that reduce malnutrition and dehydration. This may range from nil by mouth with total enteral support to full oral route or a balance of the two. Enteral feeding is essential to maintain nutritional status when oral feeding is suspended, even if only for a short time. Prompt involvement of a dietitian is thus essential.

Treatment of Crohn’s disease is based on the disease site, pattern, activity, and severity. The general goals of treatment for Crohn’s disease are as follows:
To achieve the best possible clinical, laboratory, and histologic control of the inflammatory disease with the least adverse effects from medication.
To permit the patient to function as normally as possible.
Therapy for mild Crohn’s disease is typically administered in a sequential “step-up” approach, in which less aggressive and less toxic treatments are initiated first, followed by more potent medications or procedures if the initial therapy fails.
Patients are treated with preparations of 5-aminosalicylic acid (5-ASA), antibiotics, and nutritional therapy. However, the use of 5-ASA for the treatment of Crohn’s disease is controversial; only a small subset of patients may benefit from this agent. Although 5-ASA is effective for reducing disease activity in active Crohn’s disease, it typically has a lower efficacy for Crohn’s disease than for ulcerative colitis, and its efficacy for maintenance of remission remains unproven.

If no response occurs or if the disease is more severe than initially thought, corticosteroids and inhibitors of DNA synthesis (i.e., immunomodulators) with 6-mercaptopurine (6-MP)/azathioprine or methotrexate are administered. Finally, biologic agents (infliximab, adalimumab, certolizumab pegol, and natalizumab) and surgical therapies can be useful.

For the treatment of moderate to severe Crohn’s disease, current recommendations include the “top-down” approach, which differs from the conventional step-up approach in that more potent agents are administered initially. Top-down therapies include biologic agents and steroids as needed versus combination therapy with both biologic drugs and immunomodulatory agents.

Azathioprine or 6-MP is effective for maintenance of remission in Crohn’s disease; each is effective for avoiding surgery and for preventing postoperative and endoscopic relapse. Both agents can be used in combination with infliximab.

If medical therapy for active Crohn’s disease fails, surgical resection of the inflamed bowel, with the restoration of continuity, is indicated.

Recommended indications for surgical intervention include the following:
Failed medical therapy
Persistent symptoms despite high-dose corticosteroid therapy
Treatment-related complications, including intra-abdominal abscesses
Medically intractable fistulae
Fibrotic strictures with obstructive symptoms
Toxic megacolon
Intractable haemorrhage
Perforation
Cancer

For Rectal Crohn’s: Proctectomy is appropriate, and in published series, it is required in 10 to 20% of cases. Unfortunately, proctectomy can be complicated by poor wound healing and perineal sinus formation in up to 25 to 50% of patients. A gracillis flap can be helpful.

90 – 95% of the bile salts are absorbed from the small intestine (mostly terminal ileum and then excreted again from the liver. This is known as the enterohepatic circulation. The entire pool recycles twice per meal and approximately 6 to 8 times per day.