Liver: Structure and function

 

Function: 

•Synthesis and secretion of proteins (albumin / clotting factors)

•Removal of toxic metabolites

•Secretion of bile to aid digestion and absorption of fat soluble vitamins (ADEK)

•Storage of glycogen and secretion of glucose

Structure: The basic anatomical unit of the liver is the lobule. Hepatocytes are arranged in one cell thick interlocking chains radiating from a central vein. The  vascular spaces between  the hepatocytes are known as sinusoids. Sinusoids are lined with fenestrated endothelium allowing free contact with the blood contents and hepatocytes.

Blood flow and portal tract:  Blood enters the sinusoids via the portal tract (consisting of portal vein, portal artery and bile duct).  Blood flows through the sinusoids (allowing communication with the hepatocytes) and into the central vein of that lobule which eventually feeds in to the hepatic vein and the IVC.

Space of Disse:  The space between the fenestrated endothelium and hepatocytes is called the space of Disse. Within this space are the Kupffer cells of the reticuloendothelial system. These provide a defence against pathogens and toxins in the portal venous blood flow and also contribute towards scarring in cirrhosis.

Bile : There is a network of bile canaliculi running closely along the hepatocytes which drain into the bile ducts in the periphery of the lobule. Note, they drain in the opposite direction to blood flow.

Testing for H-pylori infection



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The common tests are:

1.Serological testing

2.Urea breath test

3.Biopsy based urease

4.Histology

5.Microbial culture

 

 

 

 

 

1/ This detects antibody (IgG) response to H.pylori antigens. This confirms exposure at some point but will not discriminate between current or previous exposure. Therefore it can not be used to follow up eradication therapy.

2/This relies on bacterial urease activity in the stomach which is only found if H.pylori is present. Radiolabelled urea is ingested and is then broken down by the urease. Radiolabelled carbon dioxide is released into the blood and subsequently exhaled.  This test can be used to asses active infection but has time and cost implications in primary care.

3/This uses the same principle as the urea breath test. Tissue biopsy containing urease is placed in a urea solution. Ammonia is released which raises the pH of the solution which is detected by an indicator. This is the basis of the CLO (campylobacter like organism) test. A major diadvantage of this test is that it involves an invasive endoscopic procedure.

4/This requires visualisation of H.pylori adherent to the gastric mucosa. The bacteria can be directly viewed using HandE staining. Alternatively, specific stains or immunological techniques can be used. Disadvantage: the test is invasive. Advantage:  culture and sensitivity to the most commonly used agents (clarithromycin and metronidazole) can be performed.

5/Faecal antigen testing requires the detection of H.pylori antigens shed from live bacteria into the gut lumen.

Duke's staging of colorectal cancer



training.seer.cancer.gov



A: Tumour which does not extend beyond muscularis propria (layer of circular and longitudinal muscles) à 97% five year survival

B: Tumour extends across muscularis propria with no nodal involvement à 80% five year survival but dramatically worse prognosis if locally invasive

C1: Full thickness growth. Only a few nodes are involved near the primary growth  and the proximal nodes are free from metastasis à 60% 5 year survival

C2: Proximal nodes are involved à 30% five year survival

D: Distant metastasis à <5% 5 year survival

The 4 classical presentations of glomerulonephritis.

This is a notoriously complicated topic. However, a basic appreciation of the major presentations of glomerulonephritis should suffice for final exams.

1-Acute nephritic syndrome

2-Asymptomatic haematuria and / or proteinuria

3-Nephrotic syndrome

4-Chronic renal failure

1/ The acute nephritic syndrome is manifest by haematuria, hypertension, oliguria, proteinuria and sometimes oedema. This is most often seen with either acute proliferative glomerulonephritis (often post streptococcal) or diffuse proliferative crescenteric glomerulonephritis (seen in systemic vasculitis and rarely anti GBM disease).

2/This is typical of IgA nephropathy when recurrent heavy haematuria can occur following URTI. Asymptomatic proteinuria can also be seen with IgA nephropathy or the membranoproliferative glomerulonephritides.

3/ Characterised by heavy proteinuria (>3.5g day), hypoalbuminaemia, oedema and hypercholesterolaemia. This is most commonly associated with minimal change disease in children and membranous glomerulonephritis in adults.

4/  Chronic renal failure from glomerulonephritis may follow from symptomatic acute nephritic syndrome eg due to systemic vasculitis with crescenteric glomerulonephritis or it may follow on from the recurrent haematuria of IgA nephropathy. Chronic renal failure with significant elevations of urea and creatinine may also be diagnosed de novo and be due to the progression of preexisting glomerulonephritis. In some cases a diagnosis cannot be made because the end stage atrophic kidneys preclude diagnosis.

glufkids.com
A child with nephrotic syndrome

The vestibular system: structure and function.

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•The inner ear consists of a bony capsule known as the ‘otic capsule’ within the petrous portion of temporal bone. Anteriorly there is the snail like cochlear, in the middle there is the vestibule and posteriorly the three semicircular canals.

 

•The otic capsule is filled with fluid known as perilymph and suspended in the perilymph is a membranous labyrinth. These are delicate arrangements of sacs and tubes filled with a different fluid known as endolymph.

 

•The three membranous semicircular canals which occupy the corresponding bony structures are known as the anterior, posterior and horizontal semicircular canals. They are set at right angles and each represent a plane in space.

 

•The anterior end of each canal is dilated to form its ampulla. This contains a patch of neuroepithelium called the crista. The hairs of the crista are displaced following angular acceleration in that plane which triggers signal transduction along the vestibular nerve. 

 

•The canals come together at the vestibule which contains two further  significant regions; the utricle and the saccule. These contain a patch of neuroepithelium known as the macula. The macula contain calcium carbonate particles called  otoliths  and these are used to detect gravitational pull  (utricle) and linear acceleration (saccule).

 

•Nerves from the ampulla, utricle and saccule unite to form the vestibular nerve, the ganglion of which lies in the internal auditory meatus.

 

•Vestibular fibres from cranial nerve VIII terminate  in the vestibular nucleus in the medulla oblongata.  Axons then run to numerous areas of the CNS such as the spinal cord, the cerebellum, the cerebral cortex and the nuclei controlling extrinsic eye muscles. Fibres also communicate with the cerebellum to fine tune movement.

 

The acute red eye



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Acute angle closure glaucoma: Characterised by sudden onset painful red eye with vomiting from pain, halos seen around lights, decreased visual acuity due to corneal oedema, semi dilated  non reactive pupil and stony hard eyeball. There may be a history of intermittent subacute attacks. THIS IS AN OCULAR EMERGENCY which requires immediate treatment (iv acetazolamide, topical treatment and laser iridotomy).

Keratitis: This is inflammation of the cornea. Can be viral, fungal, bacterial or due to acanthoemeba (as seen in contact lens wearers). Presentation: unilateral photophobia, blurring, pain, eyelid oedema, discharge, hypopyon, dendritic ulcer (HSV) and stromal precipitates.

Conjunctivitis: This is inflammation of the conjunctiva. It can be bacterial, viral, chlamydial or allergic.

  Simple bacterial conjunctivitis:  subacute onset, bilateral, burning + discharge.  Gonococcal conjunctivitis presents with creamy discharge and oedema.

  Adenovirus: Types 8 and 19 cause contagious viral conjunctivitis. (types 3, 4 and 7 associated with pharyngitis). Acute onset, bilateral, watering, redness, discomfort and photophobia.

  Adult chlamydial conjunctivitis presents with chronic unilateral discharge. Neonatal forms may pass from mother to child. Trochoma occurs in developing world where chlamydia trochomatis is carried by the common fly à associated with scarring.

  Vernal (allergic) conjunctivitis: associated with atopy. Causes burning, photophobia, itching and characteristic cobblestone papillae.

Uveitis: This is inflammation of the uvea (iris, ciliary body and choroid together).  Can manifest as anterior uveitis (predominantly iritis), intermediate uveitis, posterior uveitis or panuveitis.  May be acute or chronic.  Presentation of acute uveitis:  unilateral, pain, photophobia, injections around the limbus, no itching, poorly reactive pupil. Signs: keratic precipitates (KPs), posterior synechiae and hypopyon. This is associated with HLA-B27 and AS.

Other things to look out for in the acute red eye include a hx of trauma, foreign bodies and operations (eg. post op endophthalmitis).

Complications of treatment for hyperthyroidism

en.wikipedia.org

1.Anti-thyroid drugs: Carbimazole and propylthiouracil. Main side effects are neutropenia but rashes are also common.

 

2.Radioactive iodine: Insufficient dosing may lead to recurrent thyrotoxicosis.  Patient may eventually develop hypothyroidism.  There is a theoretical risk of malignancy associated with radioactive iodine so it is reserved for older patients. Pregnancy is an absolute contraindication.

 

3.Surgery: usually a subtotal thyroidectomy. Complications are those associated with any surgical procedure but also: damage to recurrent laryngeal nerve leading to vocal cord paralysis, haemorrhage causing tracheal obstruction, hypocalcaemia due to parathyroid damage, thyrotoxic crisis due to release of thyroid hormone during surgery.

Symptoms and causes of hypoglycaemia



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Symptoms:

Adrenergic overactivity (sympathetic symptoms):

•Palpitations

•Pallor

•Sweating

•Nausea

•Tremor

•Anxiety

•Dilated pupils

Neurological symptoms (insufficient glucose in CNS)

•Confusion

•Difficulty in concentrating

•Slurred speech

•Personality change

•Double vision

•Seizures

•Hunger

•Coma

Causes:

Increased activity / reduced food intake / increased insulin administration / concomitant alcohol administration / excess dose of sulphonylureas especially longer acting ones such as chlorpropamide or glibenclamide when used in the elderly.