Question of the Day... Pseudomembranous colitis

This question was taken from May Edinburgh 2013 exam.

Question:

What is pseudomembranous colitis? What is the organism responsible and what is the pathophysiology?

Answer:

Pseudomembranous colitis is inflammation of the bowel associated with clostridium dificile and is a cause of antibiotic-associated diarrhoea.

Pathophysiology

The use of broad spectrum antibiotics such as cephalosporins or penicillin based antibiotics such as amoxicillin cause alteration of the normal bowel flora. The antibiotic kills off other competing bacteria in the intestine and any bacteria that remains has less competition for space and nutrients. Clostridium dificile may colonize the gut usually but when over-extensive growth due to less competition, in conjunction with toxins produced by the Clostridium dificile results in pseudomembranous colitis

Pseudomembranous colitis

The pseudomembranes on the mucosa of the colon or rectum is diagnostic. The pseudomembranes are composed of an exudate made of inflammatory debris, white blood cells.

For your information... Anti-platelet medication

There are several commonly used anti-platelet medications that are used in medical practice but for the purposes of MRCS I suggest learning about 2.

Aspirin
Inhibits the production of thromboxane A2, which then prevents further platelet aggregation at the site of a platelet plug.

Clopidogrel (Plavix)
Irreversibly inhibits an ADP chemoreceptor on platelets, also preventing further platelet aggregation at the site of a platelet plug.

For you information... Haemostasis

This question is taken from the London Feb 2013 exam.

Question:
What are the stages of haemostasis?

Answer:
Haemostasis is a process that causes bleeding to stop. There are 3 steps that occur in rapid sequence.

1. Vasoconstriction (vascular spasm): The damaged blood vessels contract as the first response to injury. This reduces blood flow to the area and limits the amount of blood loss. It is triggered by local pain receptors as well as local chemicals released by the damaged endothelial cells.
2. Platelet plug formation: Platelets adhere to the damaged endothelium to for a platelet plug and seals up the break in the vessel wall. They then release chemical mediators such as adenosine diphosphate (ADP), serotonin and thromboxane A2 that potentiate more platelets to adhere to the platelet plug.
3. Activation of the coagulation pathway: The platelet plug is reinforced by activation of the coagulation pathway and the subsequent products. Fibrinogen is converted to fibrin by thrombin. Clot regulation occurs through a negative feedback loop to prevent excessive clotting.

Mnemonics... Pancreatitis

Here is a common but neat way to remember the causes of Pancreatitis:

I - Idiopathic

G - Gallstones
E - Ethanol (Alcohol consumption)
T - Trauma

S - Steroids
M - Mumps
A - Autoimmune (SLE, RA)
S - Scorpion sting
H - Hyperlipidaemia
E - ERCP (Iatrogenic)
D - Drugs

For Your Information... Granuloma

What is a Granuloma?

A granuloma is a collection of activated macrophages!

Question of the Day... Critical Limb Ischaemia

This question is taken from the May Edinburgh 2013 Exam.

Question:
What are the diagnostic criteria for critical limb ischaemia?

Answer:
There are 3 main criteria for critical limb ischaemia.

1. Rest pain
2. Tissue loss
3. Ankle pressure of <50mmHg, ABPI <0.4, or Toe pressure of <30mmHg

Critical limb ischaemia is where the occlusion is no longer acute and the viability of the limb is threatened, requiring immediate management.

It is classically described with the 6 Ps:

Paraesthesia

Pain

Pallor

Pulselessness

Paralysed

Perishingly cold

Management of Critical Limb Ischaemia

In MRCS, the thing that you must remember is everything comes back to 1st principles. So when asked about management, first you talk about confirming the diagnosis (i.e investigations) then you talk about treatment. When talking about treatment, always start with A, B, and C.

A: Airway - intact

B: Ensure Oxygen is given

C: Ensure aggressive fluid resuscitation to avoid Reperfusion Syndrome. Place the patient on cardiac monitoring and monitor Urea and Electrolytes regularly. Consider doing an ABG and Lactate to further monitor acidosis and ischaemia

Management of CLI

In a nutshell!

Question of the Day... General Anatomy

These questions are taken from the Singapore Oct 2013 MRCS Part B OSCE Exam.

Question:

Name the 1st 2 branches of the ascending aorta.

Answer:
The ascending aorta has 2 branches, the Right and Left coronary arteries. The RCA arises from the anterior aortic sinus and the LCA arises from the posterior aortic sinus. You need to know 2 main branches from each coronary artery and what it supplies

RCA
The 2 main branches of the RCA:

1. Posterior interventricular branch
2. Right marginal branch

LCA

The 2 main branches of the LCA"

1. Anterior interventricular branch
2. Left circumflex artery

Question:

What is the course of the splenic artery?

Answer:

The splenic artery arises as one of the branches of the coeliac trunk and runs along the superior surface of the pancreas in the lienorenal ligament to the hilum of the spleen.