**1.1 Physiological changes in pregnancy**

### **1.1.1Renal function during pregnancy**

The kidney undergoes monumental physiologic and anatomic changes during a normal pregnancy. Renal plasma flow increases by 50-70%. Plasma volume increases by 50% and there is hemodilutional anemia. Cardiac output increases by 40%.Glomerular Filtration Rate (GFR) is maximum around the 13th week of pregnancy and can reach levels up to 150% of normal. Despite increased GFR the intraglomerular pressure remains normal. Serum creatinine falls by an average of 0.4 mg/dl to a pregnancy range of 0.4 to 0.8 mg/dl. Hence, a serum creatinine of 1.0 mg/dl, although normal in a non pregnant individual, reflects renal impairment in a pregnant woman. Serum creatinine rises near term and value of 1 mg/dl is considered normal. In the initial part of pregnancy there is decreased peripheral vascular resistance with a blood pressure fall of approximately 10 mm Hg in the first 24 weeks. The blood pressure gradually returns to prepregnancy level by term. Glycosuria occurs due to decrease in transport maximum for glucose(TMG) and high GFR. Aminoaciduria (2 g/d) may be seen. Increased uric acid clearance results in low uric acid level (2.5-5.5 mg/dl) but levels increase later and reach prepregnancy values at term. A value of >6 mg/dl reflects pregnancy induced hypertension (PIH). Potassium and almost 900 meq of sodium are retained. Calcium excretion increases but stone formation is not increased as there is increased excretion of inhibitors of stone formation. A reset in the osmostat occurs, resulting in increased thirst and decreased serum sodium levels ( by 5 mEq/L) and low plasma osmolality (10 m0sm/kg less ). Clearance of ADH is increased by placental vasopressinase and may result in transient Diabetes insipidus of pregnancy which may respond to DDAVP. On the other hand there are some reports of transient SIADH in pregnancy. Urine concentration and dilution are adequate. There is mild respiratory alkalosis and blood gas of 7.42-7.44/30 pCO2/HCO318-22 is representative (Chris Baylis,2007).

Acute Kidney Injury in Pregnancy 153

however, pregnancy complications characteristic of each trimester that can result in renal

ii. *Late pregnancy-*PIH and its complications, Hemolytic anemia ,elevated liver enzymes and low platelets (HELLP), Post partum Hemolytic uremic syndrome (HUS), Acute fatty liver of pregnancy, Volume loss –Antepartum hemorrhage (APH), Post partum hemorrhage

In a study carried out at Osmania General hospital ,Hyderabad ,India over a period of 8 years Obstetric renal failure accounted for 12.1% with PIH as the commonest cause accounting for 39.3%, PPH 20.7% ,Puerperal sepsis 10.6%, APH-9.2%.Septic abortion-

Severe vomiting in early pregnancy can lead to volume depletion and acute kidney injury. Metabolic alkalosis can be seen. Vomiting can be aggravated by certain triggers which include strong smells, postures which delay gastric emptying, hot foods etc. The patient may need hospitalization and volume replacement. Antiemetic drugs can be used to control vomiting. These include pyridoxine-doxylamine succinate combination therapy for initial pharmacologic treatment of nausea of pregnancy, antihistaminics, domperidone, metaclopramide, and ondensetron. Glucocorticoids have been used in refractory cases.

The commonest causative organism is Clostridium. It manifests few hours to 1-2 days after abortion with fever, vomiting and pain abdomen. Progression to shock and death is rapid. Jaundice due to hemolysis and cutaneous vasodilatation contribute to bronze skin coloration. Anemia, leucocytosis and thrombocytopenia with associated disseminated intravascular coagulation may be seen. Management consists of antibiotics and volume resuscitation. Other therapies include hysterectomy, hyperbaric oxygen, antitoxin and exchange transfusion.

Hypertensive disorders are the commonest cause of renal failure in pregnancy. These are

Terminology of hypertensive disorders varies, but following 5 entities have been described

**Gestational hypertension/ Transient hypertension** - is defined as blood pressure of 140/90 mm Hg or greater with no hypertension before pregnancy. It usually affects nulliparous females mostly in third trimester. Preeclampsia does not develop and blood pressure returns to normal levels within 12 weeks postpartum. Patients are usually asymptomatic or

seen in two settings: young primigravidas and older multiparous women.

by National High Blood Pressure Education Program (NHBPEP, 2000):

failure.

Can be divided into

(PPH), Sepsis

**Early pregnancy causes** 

**2.1.2 Septic abortion** 

**Late pregnancy causes** 

**2.1.3.1 Classification** 

**2.1.3 Hypertensive disorders of pregnancy** 

**2.1.1 Hyperemesis gravidarum** 

**2.1 Causes of renal failure in pregnancy** 

4.9%,HUS-3.4% and 11.7% were undetermined .

i. *Early pregnancy-* Hyperemesis gravidarum , Septic abortion .

Hyperemesis may recur in subsequent pregnancies. (ACOG, 2004)
