Medical Infographics

Bile acids

Role of Bile acids

Bile acids play a key role in the absorption of lipids in the small intestine.
Contribute to cholesterol metabolism by promoting the excretion of cholesterol.
Denature dietary proteins, thereby accelerating their breakdown by pancreatic proteases.
Direct and indirect antimicrobial effects. In this capacity, recent evidence suggests bile acids are mediators of high-fat diet-induced changes in the gut microbiota.
Act as signaling molecules outside of the gastrointestinal tract.

The primary bile acids—cholic acid and cheno-deoxycholic acid—are synthesized from cholesterol in the liver.

The maximal rate of bile acid synthesis is on the order of 4 to 6 g/day.

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Horseshoe Kidney

Horseshoe kidneys are often asymptomatic with incidence of approximately 1 in 500 in the normal population with a male preponderance of 2:1.

The isthmus connecting the two renal masses may be positioned in the midline or laterally resulting in an asymmetric horseshoe kidney, 70% of which are left dominant.

The isthmus consists of renal parenchyma in about 80% of cases with the remainder being composed of a fibrous band.

In more than 90% of cases, fusion occurs at the lower pole, although fusion may occur at the upper pole in a small minority of cases.

Higher incidence of UPJ obstructions, nephrolithiasis, and reflux compared to the general population. Increased frequency of some common renal cancers including transitional cell tumors (three to four times more common), Wilms tumor (twice as frequently), and an extremely large increase in very rare tumors such as carcinoid (62 to 82 times).

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Polycystic kidney disease (ADPKD)

Autosomal Dominant, M = F, by 60 yrs-50% need renal replacement therapy

Multisystem & progressive disease with cysts formation

Kidney enlargement with other organ involvement (liver∼ 80%, pancreas 7-36%, spleen)

Intracranial aneurysms in ∼6% of pts without family history & ∼20% with a family history (rupture in 65-75%, usually before age 50)

Cardiac Valve abnormalities in 25-30%

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Urinary Bladder and Micturition

First sensation of bladder filling at 100–150ml in an adult.
Feeling of need to pee at 200 - 350 ml of urine
Can comfortably hold between 300 - 450 ml
Wall pressure of 5 - 15 mm Hg creates a sensation of bladder fullness while 30 mm Hg & beyond is painful.
Most people pee 6 or 7 times/ 24 hours (4 -10 times daily is healthy).
Normal 24-hour Urine output is 800 - 2000 ml/day (at normal fluid intake of about 2 liters/day).

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Calot’s Triangle (CT)

Calot's triangle is a small (potential) triangular space at the porta hepatis of surgical importance as it is dissected during cholecystectomy. Its contents, the cystic artery and cystic duct must be identified before ligation and division to avoid intraoperative injury.

Borders

Medial – common hepatic duct.
Inferior – cystic duct.
Superior – inferior surface of the liver.

The above differ from the original description of Calot’s triangle in 1891 – where the cystic artery is given as the superior border of the triangle. The modern definition gives a more consistent border (the cystic artery has considerable variation in its anatomical course and origin).

Contents

Right hepatic artery
Cystic artery
Cystic lymph node (of Lund)
Connective tissue
Lymphatics
Occasionally accessory hepatic ducts and arteries

Significance

Cystic artery arises from Right Hepatic Artery in the Calot's triangle in 75%
Cystic artery origin & course vary in 25% of population.

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ACTH stimulation test

IV/IM admin of cosyntropin (250 μg), with collection of serum & measurement of cortisol at baseline & 30–60 min post stimulation.

Supra-physiological dose stimulates the pituitary & releases cortisol from the adrenal cortex, as long as the adrenal cortex has a functional reserve.

Factors affecting ACTH stim test interpretation:

Falsely negative or normal in mild disease or disease of recent onset.
Most common- false-positive test is seen in recent use of corticosteroids
Exogenous steroids lead to both baselines &adrenal responsiveness to cosyntropin.
Propofol impairs adrenal steroidogenesis
Midazolam, morphine, and fentanyl blunt the HPA axis, thereby interfering with corticosteroid metabolism.
Metyrapone, etomidate, ketoconazole, megesterol, & mitotate interfere with cosyntropin function.
Rifampin & phenytoin may increase cortisol metabolism.

In females, response to ACTH may be affected OCs which increase CBG levels.

Salivary cortisol response can be useful as their measurement is a surrogate for serum free cortisol & are not affected by OCs
Opioid receptors are present in the pituitary gland & hypothalamus, & opioids may impact HPA function.
Nenke et al studied 17 pts treated with long-term opioids. Five of the 17 (29%) were found to have evidence of AI, with cortisol levels of <5 μg/dL.

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Diabetes and hemoglobin A1c

In patients ≥65 years of age treated with medication for type 2 diabetes, hemoglobin A1c values of 7%–8% have shown the greatest reduction in mortality in multiple studies. The specific hemoglobin A1c target between 7% and 8% should be based on shared decision-making and the overall condition of the patient at that specific age, with goals in the lower 7% range for those with good to excellent functional status. It is suggested that lower hemoglobin A1c values are associated with frequent hypoglycemia, which presents a greater risk than a higher hemoglobin A1c value alone. Hemoglobin A1c values over 9% are associated with greater mortality. Thus, while the risk of complications increases linearly with hemoglobin A1c, mortality has a U-shaped curve. Management of blood pressure and treatment with statins improves mortality in these patients as well and is important in addressing overall cardiovascular risk.

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Xanthogranulomatous pyelonephritis

Xanthogranulomatous pyelonephritis is an uncommon, severe, subacute, or chronic suppurative process characterized by destruction and replacement of the renal parenchyma by granulomatous tissue containing histocytes and foamy cells. It is most often associated with chronic obstruction and stones with ongoing infection. It is also referred to as a pseudotumor due to an enlarged kidney resembling a tumor and the ability of local invasion and destruction.

The etiology remains unknown. However, most of the cases result from chronic urinary obstruction and infection. The organisms most commonly associated with XGP are Escherichia coli, Proteus mirabilis, Pseudomonas, Enterococcus faecalis, and Klebsiella, etc. Urinary obstruction occurs as a result of calculus, most commonly, staghorn calculus (in almost 80% of patients), which serves as a nidus for infection resulting in the destruction of the renal parenchyma.

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Sister Mary Joseph’s Nodule

Defined as neoplastic lesion in the periumbilical region arising as a primary tumor or representing as a site of metastasis from visceral organ malignancies such as from the gastrointestinal tract and the reproductive organs. The overall incidence is 1-3% in general population with malignancies. The primary site of malignancy associated is significantly different in men and women. The most common primary site in men is the stomach followed by the colon and pancreas, whereas in women, the most common site is the ovary followed by endometrium, colorectal, and pancreas.

The prognosis of patients presenting with Sister Mary Joseph’s nodule is generally poor as it is a sign of advanced malignancy. Management of the disease should consider patient preference, the clinical state of the patient, and the etiology of the primary malignancy.

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Porcelain gallbladder (PGB)

Term porcelain gallbladder (PGB) is often used to describe calcification of the gallbladder wall. When infiltrated by extensive calcium deposits, the gallbladder wall can become fragile, brittle and bluish in appearance, resulting in a ‘porcelain’ appearance.

The true incidence of porcelain gallbladder is unknown, but it is reported to be 0.6-0.8%, with a male-to-female ratio of 1:5. Most porcelain gallbladders (90-95%) are associated with gallstone. Mean age at diagnosis is 32 to 70 years.

Patients with porcelain gallbladder are usually asymptomatic, and the condition is usually found incidentally on plain abdominal radiographs, sonograms, or CT images.

Based on early studies which revealed a high association between porcelain gallbladder and gallbladder adenocarcinoma (22-30% of porcelain gallbladders developing gallbladder adenocarcinoma), cholecystectomy has been routinely performed when a porcelain gallbladder is identified.

More recent studies have cast some doubt on the association, and the risk of gallbladder cancer associated with calcification of the wall may be as low as 5-7%. There is no accepted follow-up interval, but the annual incidence of developing gallbladder cancer is likely to be <1% per year.

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Dupuytren’s contracture

Dupuytren’s contracture is predominantly a myo-fibroblastic disease that affects the palmar and digital fascia of the hand and results in contracture deformities. The most commonly affected digits are the fourth and fifth digits. It is a genetic disorder that often is inherited in an autosomal dominant fashion, but is most frequently seen with a multifactorial etiology. There are a number of factors that are believed to contribute to the development or worsening of this disease.

These include:

Men are more likely to develop the condition than women.
People of northern European (English, Irish, Scottish, French, and Dutch) and Scandinavian (Swedish, Norwegian, and Finnish) ancestry are more likely to develop the condition.
Dupuytren's often runs in families.
Drinking alcohol may be associated with Dupuytren's.
Diabetes, HIV, Vascular disease, smoking and seizure disorders are more likely to have Dupuytren's.
Incidence of the condition increases with age.

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Dual-energy x-ray absorptiometry (DEXA)

Uses x-rays at two energy levels to determine the bone mineral content.
Major role in diagnosis of osteoporosis, the assessment of patients' risk of fracture, and monitoring response to treatment.
T-score is a number of standard deviations between the patient’s mean BMD and the mean of the population compared with reference populations matched in gender and race.
Z-score is the number of standard deviations above or below the mean of age-matched controls.
DEXA could be used to measure bone density at many skeletal sites, two sites are typically measured: the first four vertebrae of the lumbar spine posteroanterior, and the proximal femur (“hip”), including the femoral neck and the trochanteric areas and total hip measurement. Femoral neck and lumbar spine are the gold standard for evaluating osteoporosis, with good accuracy and high precision.
All women 65 years and older and men 70 years and older should be screened for asymptomatic osteoporosis.

The World Health Organization (WHO) defines T-scores as: