Renal Failure

·     

Traditionally

the abrupt or gradual loss of kidney function which results in the retention of urea and other nitrogenous waste products and in the dysregulation of extracellular volume and electrolytes.

 

·        Other key terms in Renal failure:-

 

ü RIFLE – Recent criteria put for classifying Acute Kidney Injury (AKI). Risk, Injury, Failure, Loss, ESRD

ü Azotemia – accumulation of nitrogenous waste products

ü Uraemia – Clinical syndrome representing systemic effects resulting from renal failure

 

·        Renal failure can be classified into:-

 

ü Acute Kidney Injury – developing over hours to days

ü Rapidly progressive – developing over weeks to months (usually less than 3 months)

ü Chronic Kidney Disease – developing in a time more than 3 months

 

·        Acute Kidney Injury

 

ü Definition: loss of renal function, measured by a decline in GFR, developing over period of hours to days.

 

ü Causes: Prerenal, Intrinsic and post renal

o   Prerenal – due to impaired perfusion. Causes include: Hemorrhage, Diarrhea, Vigorous diuresis, burns, sepsis, cirrhosis, anaphylaxis, CHF

o   Intrinsic – actual damage to the kidneys. 40% of ARF. Causes include: prolonged prerenal causes, toxic injuries resulting from either exogenous substances (drugs, contrast agents) or endogenous substances (hemoglobin, myoglobin, urate)

o   Postrenal – obstruction to urine flow. 5% of ARF.

 

·        Epidemiology

Common; incidence of 1-25% depending on the definition used and population understudy

Mortality vary from 28-90% depending on comorbidities

Is associated with adjusted prolongation of hospital stay of 2days

·        Clinical Manifestations

 

ü Acute Kidney Injury (AKI) may impair the excretory, regulatory and endocrine functions of the kidneys and is characterized by retention of nitrogenous waste products in the blood (azotemia) and changes in urine volume

Usual scenario is patient presents with complications of AKI or picked up on routine followup for unrelated condition

·        Investigations

 

ü Urine analysis

Prerenal – acellular (bland), hyaline casts

Intrinsic – “muddy brown” granular casts

ü Serum BUN and Creatinine

ü FENa (Fractional Excretion of Sodium)

Prerenal - <1

Intrinsic - >1

ü Imaging

 

·        Complications of AKI

 

ü CVS – Fluid overload (edema), hypertension, pericardial effusion, MI, Arrrhthmia

ü Metabolic & Electrolyte disturbance – hyperkalemia, hyper/hypomagnesemia, hyperphosphatemia, hypocalcemia, hyponatremia, metabolic acidosis

ü Hematology – anemia and bleeding tendency

ü GI – Nausea, vomiting, GI ulcer, malnutrition

ü Neurology – altered mentation, asterixis, seizures, impaired cognition

ü Immunonogy – Infections (pneumonia, UTI, sepsis)

 

·        Management

 

ü Specific

o   Prerenal – correct hypovolemia

o   Intrinsic – No specific treatment

o   Postrenal – relieve obstruction

ü Supportive – towards complications

ü Prevention – attention towards volume status and caution with nephrotoxic agents

 

·        Prognosis

 

ü Mortality 50%;  Recovery 40%;  CRF 5%;  Incomplete recovery 5%

·        Prognostic factors

ü Oligo-uria at presentation

ü Serum creatinine >3mg/day

ü Old age

ü Multiple organ failure