Kidney pathology and pregnancy

2021-07-28 09:45 AM

In pregnant women, a blood creatinine level above 80 μmol per liter and a blood urea concentration above 5 mmol per liter may indicate a decrease in renal function during pregnancy.

Changes in the urinary system during pregnancy

Changes in the anatomy of the renal-urinary system during pregnancy

Renal size increases during pregnancy: on ultrasound and X-ray detection the length of the kidney increases by about 1 cm compared to before pregnancy. The size of the kidneys is normal after birth.

Pyelonephritis and ureter: often detected by ultrasound and pyelography, which indicates fluid retention due to obstruction of the urinary tract. This water retention is usually mild, called "physiological" pyelonephronodilation during pregnancy.

It has been found that during pregnancy there is a decrease in smooth muscle tone of the urinary tract system (possibly due to the role of vasodilating hormones such as Prostaglandins, Estrogenic and Prolactin) plus mechanical compression 2. The ureter due to a large uterus is the cause of this fluid retention. This stagnation of urine is a favorable condition for upstream infection, whose extent can range from an asymptomatic urinary tract infection to severe pyelonephritis. In rare cases, this stagnation of urine can cause pain in the kidneys.

Renal morphological changes can persist for up to 12 weeks after birth. Hence, the morphology of the common urinary system (not an emergency) is recommended at least 12 weeks after birth.

Renal function

Changes in kidney function can also occur during pregnancy. Compared to the absence of pregnancy, the glomerular filtration flow and renal blood flow during pregnancy increase quite early, from the first few months of pregnancy, and can reach between 30 and 50% of the price. normal value at the end of 3 months.

It is this increase in glomerular filtration flow that will increase waste production and lead to a decrease in blood creatinine levels by 35 to 44% compared with normal values.

Thus, biochemical indicators that are normally considered normal in a non-pregnant woman may still reflect a decrease in renal function during pregnancy.

In pregnant women, a blood creatinine level above 80 μmol / l (0.8 mg/dl) and a blood urea level above 5 mmol / l (13 mg/dl) may present with impaired renal function. during pregnancy (according to Marshall D. Lind Heimer and Adrian I. Katz).

Urinary protein:

Due to increased blood flow to the kidneys during pregnancy, increased urinary protein ​​output increases. With the same degree of kidney damage, during pregnancy, urinary protein ​​output is doubled.

Renal tubular function:

The total clearance and partial clearance for urate increase, causing the normal value of blood urate to decrease. Therefore, an increase in blood urate concentration above 5 mg/dl or above 298 μmol / l is suspected of pathology.

Blood tends to be slightly alkaline, pH = 7.42 - 7.44.

Changes in fluid

Oedema is a very common symptom of pregnancy.

The total amount of water in the body increases, during a normal pregnancy the mother usually gains a total weight of about 12.5 kg. The increase in total water volume ranges from 6 to 9 liters, of which 4 to 7 liters is due to increased interstitial volume and plasma.

Renal osmolality changes quite early in pregnancy, and the renal osmolality for thirst and for Vasopressin secretion is reduced by about 10 mOsmol / l each. As a result, the blood sodium concentration is reduced, the normal value of sodium in blood during pregnancy is about 130 mmol / l. Concentrations above 140 mmol / l are considered to be hypernatremia.

The rate of degradation of Vasopressin is 4 times higher than normal due to the secretion of Vasopressin’s by the placenta, especially in the later stages of pregnancy.

There are 2 morphologies that combine kidney disease and pregnancy

Kidney-urinary disease occurs in a woman who had not been pregnant

Pregnancy in a patient with chronic kidney disease.

Urinary system diseases often occur during pregnancy

Pregnancy toxicity - Pre-eclampsia

Usually occurs in women over 35 years old and pregnant with babies and in the last 3 months of pregnancy. Clinical symptoms include hypertension, proteinuria, and oedema.

The pathogenesis of fetal toxicity is not well known, but most authors agree that many factors are associated.

Genetic factors: Pre-eclampsia is more common in people of the same bloodline than in people of the same bloodline.

Immune factors: Pregnancy is considered an immunosuppressed process, in which the foetus is made up of 50% of foreign cells from the father.

Liquid factors: plasma concentrations of Aldosterone and Renine of pathological women are lower than normal women, increased susceptibility to intravenous Angiotensin infusion.

Vascular factor: decreased placenta perfusion, decreased more than 50% in diameter of the helical arteries in women with pre-eclampsia.

Tissue damage to the kidneys: mainly occurs in the glomeruli, presenting with glomerular endothelial inflammation. The glomeruli are enlarged and oedematous, with the invasion of capillary membrane and endothelial cells. Hyalin fiber deposition under the endothelium. However, immunofluorescent staining did not show immune complex deposition. This damage to kidney tissue disappears after a few weeks to 1 month.

Urinary tract infections during pregnancy

Pregnant women often develop asymptomatic urinary tract infections, which may manifest with an inflammation of the bladder or worse, pyelonephritis. Mild cystitis is often overlooked because bladder irritation symptoms are also seen when the uterus is enlarged causing bladder irritation. Pyelonephritis is often diagnosed thanks to symptoms of high fever, clear infection syndrome, low back pain, cloudy urination, ... large kidney symptoms are often difficult to detect clinically because of the presence of a large uterus.

Pregnant women should have a urine test during pregnancy to avoid missing out on an asymptomatic urinary infection, preferably a urine culture.

Acute renal failure during pregnancy

In the early stages of pregnancy, acute renal failure is often associated with severe vomiting.

At the following stage, there are many causes leading to acute kidney failure such as:

Pathology of microvascular haemolysis + thrombocytopenia.

Acute renal failure in association with acute fatty liver in pregnancy: HELLP (Haemolysis Elevated Liver enzymes Low Platelets) syndrome manifested by thrombocytopenia, haemolysis of blood vessels, increased LDH, and Transaminase.

Acute tubular necrosis or more severe necrosis of the renal cortex.

Postpartum acute renal failure: usually occurs immediately after birth for up to 3 to 6 weeks after.

The most common and common type of acute renal failure in pregnancy is acute tubular necrosis due to renal ischemia or toxicity, usually a complication of a placenta, large posterior placenta, stillbirth, or obstruction. vessels caused by amniotic fluid. When irreversible damage to the tubular cells results in renal cortical necrosis, characterized by irreversible diffuse fibrosis of the renal tubule, a very serious condition in pregnancy. period.

Pregnancy in patients with chronic kidney disease

Although patients with chronic kidney disease (glomerulonephritis, chronic kidney failure, kidney transplant, etc.) are often advised not to get pregnant due to the negative consequences of pregnancy on the health of the mother. and due to the effects of existing drugs on the foetus, but in practice, pregnancy can still occur in these patients.

The degree of renal failure at the time of pregnancy and hypertension are the two main prognostic factors for pregnancy. Therefore, active monitoring and treatment of hypertension, if any, is very important during pregnancy.

For each specific kidney disease, pregnancy has the following effects:

Kidney disease caused by diabetes

Pregnancy does not increase kidney failure, but the possibility of urinary infections is quite high, increased urinary protein ​​, and increased blood pressure, especially in the last months.

Chronic glomerular disease

Pregnancy increases blood pressure but is well tolerated if the patient has no hypertension and no kidney dysfunction before pregnancy.

Many authors believe that the types of fibrosis glomerulonephritis, IgA glomerulonephritis, and membrane proliferative glomerulonephritis will worsen during pregnancy.

Renal disease due to reflux and chronic pyelonephritis

These patients are well adapted to pregnancy if there are no renal failure, however routine urine cultures (every 2 to 3 weeks), antibiotic therapy is required if necessary.

Polycystic kidney disease

Very well-tolerated without renal failure. During pregnancy the liver cysts may increase in size, increasing the incidence of hypertension and pre-eclampsia.

Kidney stones

Well tolerated, except for an increased incidence of urinary tract infections. Stones can be moved by dilating the urinary tract.

Pregnancy in haemodialysis patients

With this group of patients, despite close monitoring, obstetric complications are still very high, with the risk of death for mother and foetus, mostly miscarriage and premature birth, if the baby is born, there is also a risk. high in mental development (Susan H Hou). Therefore, the question of whether to continue to maintain a pregnancy or not in this group of patients is frequently raised.

Pregnancy in kidney transplant patients

For women with end-stage chronic kidney failure, a kidney transplant is the best method to give them hope of having a baby. However, since these patients are frequently required to take immunosuppressants and corticosteroids, pregnancy must be carefully monitored by nephrologists.

Treatment of kidney-urinary diseases often occurs during pregnancy

Treatment of toxicosis in pregnancy - Pre-eclampsia

Admission to the hospital, follow-up specialist in obstetrics and gynaecology.

Hypotension: The most important problem in pre-eclampsia treatment. Often use vasodilators or Alpha methyldopa, avoid using diuretics and ACE inhibitors.

Magne Sulphate: A classic drug in eclampsia, it works to reduce the frequency of seizures and prevent seizures during eclampsia.

Usage: Initial loading dose is 4g to 6g intravenous infusion over about 15 minutes, then intravenous infusion 2g per hour to maintain the blood magnesium concentration in the range of 4 to 6 mmol / l. In milder cases, no eclampsia manifestations can be administered intramuscularly.

Termination of pregnancy: As a last resort.

Prevention: Periodic pregnancy check-up, careful monitoring of blood pressure, Proteinuria. Patients at high risk must be examined at least once every 2 weeks, after which, if pregnancy toxicity persists, hospitalization should be followed in the following months of pregnancy.

Treatment of urinary tract infections during pregnancy

Treatment of patients with bacteriuria but clinically asymptomatic: use a course of antibiotics within 7 to 10 days.

Board. Antibiotics are often used to treat asymptomatic urinary tract infections and cystitis during pregnancy.




500 mg 4 times / day


250 mg x 3 times / day


50 mg 4 times / day


250 mg x 2 times / day

Amoxicillin/A. Clavulanic

250 / 62.5 mg 3 times / day

Treatment of acute pyelonephritis:


Immediately use intravenous antibiotics.

Usually start with Ampicillin or 3rd generation Cephalosporine (Ceftriaxone, Cefotaxime, ...).

When the clinical condition improves, after 1 to 2 weeks can switch to oral and must continue antibiotic treatment for at least 2 to 3 weeks.

Follow-up with urine culture every 2 to 3 weeks to prevent a recurrence.

Treatment of acute renal failure during pregnancy

Treatment for acute renal failure in pregnancy is in principle no different from the treatment of acute renal failure other than pregnancy, including:

Well maintained hemodynamic ensures adequate renal perfusion.

Diuretics: Caution should be exercised in cases of hypotension.

Adjust electrolyte disturbances and acid-base balance.

Renal dialysis when needed: artificial kidneys often are used because peritoneal dialysis cannot be used during pregnancy.

Combining Internal Medicine - Obstetrics to solve the cause (stillbirth, placenta detachment, ...).

Attitude for management before pregnancy occurs in chronic kidney disease

Prophylaxis: It is recommended that patients should not become pregnant in patients with chronic kidney disease, especially those with chronic renal failure. Use common methods of birth control.

Pre-pregnancy treatment attitude occurred in 1 patient with chronic kidney disease:

Active monitoring and treatment of hypertension, since increased blood pressure and degree of renal failure at the time of pregnancy, are two main prognostic factors for pregnancy:

For patients who have not had chronic renal failure: pregnancy can occur completely normally, but patients should be carefully monitored in the Obstetrics and Internal Medicine environment, it should be noted that drugs are being used for a long time. kidney disease treatment such as corticoids, immunosuppressants, antidiabetic drugs, some high blood pressure medications can affect the pregnancy.

In patients who already have chronic renal failure, the severity of the kidney failure is dependent, but these patients are often unable to keep the pregnancy, especially if the failure is severe. The risk is very high in patients undergoing cyclic dialysis treatment, and should not be kept pregnant.

For patients who have had a kidney transplant:

For women with end-stage chronic kidney failure, a kidney transplant is the best method to give them hope of having a baby. However, since these patients are frequently required to take immunosuppressants and corticosteroids, pregnancy must be carefully monitored by nephrologists.

Pre-pregnancy criteria in kidney transplant patients:

Time after transplant: 1.5 years for living kidney transplant, 2 years for a dead kidney transplant.

No rejection for at least 6 months.

Prednisone dose <15 mg / day.

 Azathioprine < 2 mg/kg.

Cyclosporine dose 2 - 4 mg / kg.

Blood creatinine concentration <2 mg / dl.

Blood pressure <140/90 mmHg (maybe taking antihypertensive drugs).

The HbA1C concentration is normal.

Negative urine cultures.

In summary, patients with kidney disease can be able to conceive and have a normal child if they do not have kidney failure and must be closely monitored with their blood pressure. For people with kidney failure, the risk of pregnancy is greater if the kidney failure gets worse. In patients with end-stage chronic renal failure, pregnancy should only be performed after a kidney transplant and should be placed under the close supervision of the nephrologist and obstetrician.