Showing posts with label Nephrology. Show all posts
Showing posts with label Nephrology. Show all posts

Saturday, April 15, 2017

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Emphysematous pyelonephritis - Review

 DEFINITION 
Emphysematous pyelonephritis is an acute necrotizing infection characterized by gas formation.
It is characterized by the presence of gas in and around the kidney.

 ETIOLOGY 
E. coli (58%) and K. pneumoniae (21%) are the organisms most commonly isolated. Clostridium and Enterobacter spp may also be responsible, 7% each.

 RISK FACTORS 
1) Diabetes mellitus (70-90%)- usually patients with poor glucose control. High levels of glucose in the urine serve as a substrate for these bacteria and large amounts of gas are generated through natural fermentation
2) Obstruction (25-40%)- it is another common predisposing factor for emphysematous pyelonephritis.

For non-diabetics, protein fermentation is a proposed source of gas formation.

 CLINICAL FEATURES 
7% of cases may be asymptomatic.
If symptomatic, patients may complain of pneumaturia, irritative lower tract voiding symptoms, flank pain or may present in a severe septic condition with an acute abdomen and high grade fever.

 DIAGNOSIS 
1) Plain radiograph of the abdomen can help us in 80-85 % of cases.
2) CT is considered the optimal imaging technique for confirming emphysematous infection and characterizing the extent of involvement.

According to radiological findings and CT scans, emphysematous pyelonephritis can be classified as follows:
Class 1— gas confined to the collecting system
Class 2— gas confined to the renal parenchyma alone
Class 3A— perinephric extension of gas or abscess
Class 3B— extension of gas beyond the Gerota fascia
Class 4— bilateral EPN or EPN in a solitary kidney
Emphysematous pyelonephritis

 Plain abdominal radiograph showing presence of air around the left kidney

Emphysematous pyelonephritis
 CT scan showing left emphysematous pyelonephritis with presence of gas and parenchymal destruction
Emphysematous pyelonephritis
CT scan of a diabetic patient with emphysematous pyelonephritis due to uncontrolled diabetes and renal stones.


 MANAGEMENT 
1) Medical management includes antimicrobial therapy, bladder drainage and glycemic control.   effective.
2) Surgical intervention usually is required for only 10% of the cases. Emergency nephrectomy was traditionally considered necessary but currently, percutaneous drainage is the recommended initial approach.

 Later, elective nephrectomy may be required for some patients.


First published on: 15 April 2017

Thursday, June 21, 2012

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Arteriovenous fistula - AVF


Definition:
It is an abnormal communication between an artery and a vein (or veins). It may be
1) a congenital malformation,
2) acquired by the trauma of a penetrating wound,
3) iatrogenic in which AVFs are created surgically in the arms or legs of patients undergoing renal dialysis. All arteriovenous communications have a structural and a physiological effect.

Structural effect:
The veins become dilated, tortuous and thick walled (arterialised).

Physiological effect:
There is high-pressure from the arterial system and an enhanced venous return/venous pressure. This results in an increase in pulse rate and cardiac output. The pulse pressure is high if there is a large and persistent shunt. Left ventricular enlargement and later cardiac failure may occur.
A congenital fistula in the young may cause overgrowth of a limb.
In the leg, indolent ulcers may result from relative ischaemia below the short circuit.

Clinical features:
Clinically, a pulsatile swelling or dilated tortuous veins may be present if the lesion is relatively superficial.
On palpation, a thrill is detected and auscultation reveals a buzzing continuous bruit.

Nicoladoni’s (1875) or Branham’s (1890) sign
Pressure on the artery proximal to the fistula causes the swelling to diminish in size, the thrill and bruit to cease and the pulse rate to fall. The pulse pressure also returns to normal.

Arteriography:
Arteriography confirms the lesion, which is noteworthy for the speed with which venous filling occurs. It is often difficult to pinpoint the actual site of the fistula.

Treatment:
Embolisation by the radiologist or excision is advocated only for severe deformity or recurrent haemorrhage. A plastic surgeon can also help for a proper ablation and reconstruction. Ligation of a ‘feeding’ artery is of no lasting value and is likely to be detrimental as it may preclude treatment by embolisation.

Clinical implications:
1) Autogenous AV fistulas have a lower risk of failure and require less revision compared to prosthetic grafts. The only problem with this is that a large number of patients lack suitable veins. This inability to make a proper vascular access is often termed as the Achilles tendon of hemodialysis. 

Wednesday, January 18, 2012

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Hemodialysis - when to start? / Calculation of normalized eGFR


Hemodialysis should be started when:
1) eGFR is < 6 mL/min/1.73 m2
2) eGFR is < 15 mL/min/1.73 m2  and patient is showing signs and symptoms of uremia, unable to control his hydration and blood pressure. 

Cockcroft-Gault formula is a very commonly used formula to get an estimate of the GFR. The unit for eGFR is  mL/min. The classification for stages of chronic kidney diseases on the other hand is based on normalized eGFR i.e. the eGFR per 1.73 m2 and the unit being mL/min/1.73 m2.


Thus we also need to calculate the surface area of the patient's body. It is given by the formula as follows : 

Body Surface Area (m2) = ( [Height(cm) x Weight(kg) ]/ 3600 )½

And the normalized eGFR (mL/min/1.73 m2) = (eGFR/BSA) x 1.73

A clinical example is given below. 
A 45 year old man weighing 70 kg and 180 cm tall has been admitted to the hospital because of fluid overload. He has been treated for the past hours with diuretics but has not been improving. Blood results showed that the serum creatinine level was 550 μmol/LShould the patient be dialysed?

a) the eGFR acc to Cockcroft formula = 14.87 mL/min.
b) the BSA of the patient = 1.87 m2

Thus the normalized eGFR = 13.76 mL/min/1.73 mwhich is indeed an indication for dialysis.

Friday, July 15, 2011

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Stages of Chronic Kidney Diseases


The table above shows how chronic kidney diseases are classified.

Risk factors include hypertension, diabetes mellitus, autoimmune disease, older age, African ancestry, a family history of renal disease, a previous episode of acute renal failure, and the presence of proteinuria, abnormal urinary sediment, or structural abnormalities of the urinary tract.

Stage 0
Not commonly included in many classifications but in this stage there is no kidney damage evident but patients have one or more risk factors mentioned above.

Stage 1
Kidney damage is there demonstrated by persistent proteinuria, abnormal urine sediment, abnormal blood and urine chemistry, abnormal imaging studies but GFR i.e kidney function will be normal.

Stage 2
Kidney damage is there and slight decrease in kidney funtion.

Stage 3-5
The older term chronic renal failure corresponds to these stages. It is characterized by a progressive, significant and irreversible kidney damage with a GFR < 60 for 3 months or more that eventually will result into End Stage Renal Disease (ESRD) i.e. stage 5.

In stages 1 to 3, the causes of the CKD are treated along with some lifestyle modifications.
In stage 4, treatment is continued along with preparation for kidney replacement therapy.
In stage 5, replacement therapy is essential for survival.

Thus if we use Cockcroft-Gault formula to estimate the creatinine clearance for a 45 year old male weighing 70 Kg, we should start preparing for kidney replacement therapy if his creatinine level reaches 270 μmol/L.
Dialysis to be done for survival if the creatinine level reaches 530 μmol/L or more.

Monday, May 9, 2011

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Cockcroft-Gault formula

It is a formula used to get an estimated creatinine clearance. It goes as follows:

eC_{Cr} = \frac { \mbox{(140 - Age)} \ \times \ \mbox{Mass (in kilograms)} \ \times \ {Constant} } {\mbox{Serum Creatinine (in } \mu \mbox{mol/L)}}

Creatinine clearance : mL/min
Age : years
constant : 1.23 for males, 1.04 for females

normal range:
men : 90 - 140 mL/min
women : 80 - 125 mL/min