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Renal Failure
Objectives:

1. To understand the types and causes of renal failure

2. To understand the management of renal failure

It is divided into 2 types:

1. Acute kidney injury was called acute renal failure

2. Chronic kidney disease was called chronic renal failure

Acute kidney injury (AKI)

AKI is defined as a rapid reduction in renal function characterized by progressive

azotemia (best measured clinically by serum creatinine and blood urea nitrogen
[BUN]), which may or may not be accompanied by oliguria.

Practice guidelines proposed by Kidney Disease: Improving Global Outcomes

(KDIGO) defined AKI when one of the following criteria was met:

1. An increase in serum creatinine greater than or equal to 0.3 mg/ dL within 48

hours

2. An increase in serum creatinine greater than or equal to 1.5 times baseline

within the previous 7 days

3. Urine volume less than or equal to 0.5 mL/kg/hr for 6 hours

Classification of Acute Kidney Injury

It is clinically useful to separate the causes of AKI into three major categories:

prerenal, intrarenal, and postrenal.

Prerenal AKI: the perfusion of the kidneys is compromised by:

1. Hypotension and hypovolemia due to vomiting, diarrhea, pancreatitis, burns,
or sweating) may be present.

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2. Heart Failure
3. Patients may have intense vasoconstriction due to hypercalcemia,
prostaglandin inhibition (eg, due to nonsteroidal anti-inflammatory drugs
[NSAIDs]), cyclosporine, ACE inhibition,

Intrarenal ( Parenchymal ) AKI.

 Nonspecific ( acute tubular necrosis and acute cortical necrosis)
 Specific ( GN., interstitial nephritis, Toxin, dye induced and haemolytic
uremic syndrome)

Postrenal AKI.
The causes are mainly obstruction to urine flow so:
The obstruction may be
– distal to the bladder ( bladder outlet obstruction, BOO)
– or bilateral ureteric
– Unilateral in case of solitary anatomical or functioning kidney

The most common cause is secondary to BOO due to BPH or a urethral stricture
Urine output findings can be misleading.
Renal ultrasound is a quick and noninvasive study that can help detect obstruction.

Classifying AKI as oliguric or nonoliguric based on daily urine excretion may be

useful. Oliguria is defined as a daily urine volume of less than 500 mL/d. Anuria is
defined as a urine output of less than 50 mL/d and, if abrupt in onset, is suggestive
of obstruction.

Treatment of AKI
It is based on its cause. Maintenance of volume homeostasis and correcting
biochemical abnormalities remain the primary goals of treatment , Correcting
acidosis with bicarbonate administration , Hyperkalemia, which can be life-
threatening should be treated, Correcting hematologic abnormalities , Dietary
modulation is very important. Simple procedures to relieve the obstruction such as
catheter placement, lithotripsy, prostatectomy, stent placement, or percutaneous
nephrostomy can help prevent permanent renal damage.

 Indications for dialysis in patients with AKI are as follows:

1. Volume expansion that cannot be managed with diuretics
2. Hyperkalemia not responding to medical treatment
3. Correction of severe acid-base disturbances

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4. Symptoms of uremic pericarditis, gastritis, seizures, or

encephalopathy
5. selected poisonings and certain drug overdoses.
Notes

Uremia: a syndrome of clinical and metabolic abnormalities associated with fluid,

electrolyte, and hormone imbalances, which develop in parallel with deterioration
of renal function. The term uremia literally means urine in the blood. In general,
uremia is associated with chronic kidney disease but it also may occur with acute
kidney injury if loss of renal function is rapid.
Azotemia is elevation of the blood urea nitrogen (BUN) (reference range = 8-20
mg/dL) and serum creatinine (normal value = 0.7-1.4 mg/dL) levels.

Average GFR is about 125 mL/min (10% less for women) or 180 L/d. About 99%
of this is reabsorbed (178 L/d), the rest (2 L/d) is excreted as urine.

CHRONIC KIDNEY DISEASE

Should be defined as sustained kidney injury longer than 3 months resulting in a

GFR of less than 60 mL/ min/1.73 m2.

Or defined as abnormalities of kidney structure or function, present for more than 3

months, with implications for health.

Classification:
CKD is classified based on cause, GFR category, and albuminuria category
(CGA).

Causes:

1. Diabetes mellitus 38%

2. Hypertension 25%
3. Glomerulonephritis 14 %
4. Cystic kidney disease 5 %
5. Urologic 2%
6. Unknown/Missing/Other 15%

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Glomerular Filtration Rate Categories in Chronic Kidney Disease

GFR GFR TERMS

CATEGORY (mL/min/1.73
m2 )
G1 ≥90 Normal or high

G2 60-89 Mildly decreased*

G3a 45-59 Mildly to moderately decreased
G3b 30-44 Moderately to severely decreased
G4 15-29 Severely decreased
G5 <15 End stage renal disease

Albuminuria Categories in Chronic Kidney Disease

CATEGORY Albumin excretion rate, TERMS

AER (mg/24 hr)
A1 <30 Normal to mildly increased
A2 30-300 Moderately increased
A3 >300 Severely increased

Renal Function Assessment

 s. creatinine but Total CrCl usually exceeds the GFR because of tubular
secretion, whereas
 the urea clearance is usually lower than the GFR because of tubular
reabsorption.
 GFR measurements (inulin or iothalamate), and cystatin C all provide
information on the level of renal function. Although the iothalamate GFR is
the “gold standard” for measuring renal function, this test is not widely
availabl
 The Modification of Diet in Renal Disease (MDRD) (http://
www.mdcalc.com/mdrd-gfr-equation/) and CKD-EPI (http://www.

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qxmd.com/calculate-online/nephrology/ckd-epi-egfr) equations are widely

used throughout the world to estimate CrCl

Medical Care:
 Medical care of uremia.
 Renal replacement therapy can be accomplished by hemodialysis, peritoneal
dialysis, or renal transplantation.

Surgical Care: Surgical referral is necessary for dialysis access placement after
the decision regarding dialysis has been made. Dialysis access can be conducted
through central venous double lumen catheter and arteriovenous shunt or fistula for
hemodialysis or a peritoneal dialysis catheter for chronic ambulatory peritoneal
dialysis or continuous cycling peritoneal dialysis.
 Arteriovenous fistulas are the dialysis access of choice for hemodialysis but need
time for maturation during which the double lumen catheter is used for
hemodialysis.
Peritoneal dialysis access can be accomplished by the placement of Tenckhoff
peritoneal dialysis catheter.