Urolithiasis in Pregnancy - Management Challenges

Introduction:

Kidney stones do occur commonly in the general population and may occur even in pregnant women. The changes in pregnant women may lead to the development of kidney stones. Ten percent of the population will be affected by kidney stones in their lifetime. This condition can also be seen in pregnant women. 1 in 200 - 1500 pregnant females may get kidney stones.

What Is Urolithiasis?

Kidney stones are usually formed in the kidneys. This condition is known as nephrolithiasis. Stones that are present in the ureter are called ureterolithiasis. Urolithiasis refers to stones that are present in any part of the urinary tract.

Kidney stones are formed due to the accumulation of chemical substances dissolved in the urine. When the concentration of these chemical substances reaches a particular point, they crystallize to form stones.

The condition of urolithiasis occurs when stones in the kidney leave the site and enter the remainder of the urinary collecting system. The remainder of the urinary collecting system includes the ureter, bladder, and urethra.

There are different types of kidney stones.

• Calcium oxalate or phosphate (80 %).

• Uric acid (9 %).

• Struvite (10 %).

• Cysteine (1 %).

The most common type of stone is calcium oxalate or phosphate.

The causes of kidney stones include diet, climatic changes, and a rise in comorbidities like diabetes and obesity. These stones occurred equally among males and females in recent years, whereas this condition was more commonly seen among males than females.

Urolithiasis in Pregnant Women:

Urolithiasis can be observed among pregnant females as well. This condition may pose health risks to the mother and the fetus. Urolithiasis among pregnant women is on the rise, especially in industrialized societies.

Urolithiasis among pregnant women may lead to urinary stasis. This may, in turn, cause complications like preterm birth and spontaneous abortion associated with urinary tract infections and pyelonephritis among pregnant females.

What Are the Changes Occurring in the Renal Tract During Pregnancy?

Changes that are observed in the renal tract during pregnancy include

• Dilatation of the pelvicalyceal system and ureters occurs.

• During pregnancy, increased smooth muscle relaxation and decreased peristalsis can be observed due to increased progesterone levels.

• An enlarged uterus, especially in late pregnancy, compresses the ureter.

• Physiologic hydronephrosis may be seen in 90 % of pregnant women.

• During pregnancy, renal plasma flow and glomerular filtration rate increase by over 50 %.

The most common cause of nonobstetric hospital admissions during pregnancy is acute urolithiasis. Changes in pregnant females' anatomical and pathophysiological structures occur and are responsible for altering the urinary environment.

How Do Kidney Stones Form?

During pregnancy, because of an increase in renal plasma flow and glomerular filtration rate, there is an increase in urinary excretion of calcium, uric acid, sodium, and oxalate. These are lithogenic. Due to suppressed parathyroid hormones, calcium tubular reabsorption is reduced. These changes and urinary stasis due to hydronephrosis promote the formation of kidney stones during pregnancy.

The risk of stone formation is similar among pregnant and nonpregnant women. This may be due to increased urinary excretion of substances like citrate, magnesium, and the glycoprotein nephrocalcin, called stone formation inhibitors. Another reason for the stone formation is the alkalinity of the urine during pregnancy.

In the general population, 80 % of stones are of the calcium type. Calcium-type stones are also common among pregnant women. Calcium phosphate stones are more common among pregnant women than in the general population, where calcium oxalate is more common.

Increased progesterone levels and mechanical compression lead to urinary stasis. Other factors like increased glomerular filtration rate, calcium supplementation, and increased vitamin D levels in the circulation cause increased urinary pH and hypercalciuria. Urinary excretion of lithogenic factors like uric acid, sodium, and oxalate is higher among pregnant women.

What Are the Risk Factors for the Formation of Kidney Stones?

Kidney stones affect 5-15 % of the world's population. The recurrence rate is around 50 %. Kidney stones are on the rise due to various factors related to lifestyle, which may lead to diseases like obesity and metabolic diseases.

Risk factors include,

• A positive history in the family.

• Dietary factors like low intake of water and increased intake of animal proteins and sodium.

• Environmental factors like hot climatic conditions.

• Associated Medical conditions like hyperparathyroidism.

What Are the Symptoms Related to Urolithiasis in Pregnancy?

Kidney stones are solids that develop when other materials in the urine bind with calcium. These cannot pass through the vessels that carry urine from the kidney to the bladder. Kidney stones block the vessels, and symptoms appear as a result.

Symptoms due to kidney stones among pregnant females include,

Pain During Urinating: The pain is of a sharp type and makes urinating unbearable for pregnant women.

Nausea and Vomiting: Pregnant females feel discomfort due to kidney stones and the build-up of urine in the kidneys.

Presence of Blood in the Urine: Due to kidney stones, hematuria (presence of blood in the urine) may develop.

Pain in the Abdomen or the Back: The pain in the abdomen or the back may be due to a -cup of urine in one or both kidneys due to blockage caused by kidney stones.

Complications of urolithiasis among pregnant women include

• Preterm delivery.

• Preterm labor.

• Premature rupture of membranes.

• Often, the loss of pregnancies.

• Preeclampsia.

These risks pose difficulties in diagnosing urolithiasis in pregnant women.

How to Diagnose Urolithiasis in Pregnancy?

Urolithiasis can be diagnosed using the following methods:

• Renal ultrasound is a standard diagnostic test for urolithiasis among nonpregnant women.

• Computed tomography is not a diagnostic tool as it may cause teratogenic causes and childhood malignancies.

• Ultrasound can be used but is less sensitive. Transvaginal ultrasound may help evacuate the distal ureter.

• Half Fourier Single Shot Turbo Spin Echo (HFSTE) magnetic resonance urography (MRU) is safe and effective without contrast.

• Low-dose CT (computed tomography) can be used. This method is highly sensitive and specific.

• Other methods are plain radiography, intravenous urograms, nuclear medicine scans, and magnetic resonance imaging.

These methods have limitations and risks for pregnant women.

White et al. showed a negative ureteroscopy rate of 14 %. This means that 1 in 7 of those who underwent the operation did not show stones.

How to Treat Urolithiasis Among Pregnant Women?

Urolithiasis can be treated with a multidisciplinary approach. Urology and obstetrics must communicate with each other.

Conservative Management

This method uses a trial of passage with hydration and analgesia. Nonsteroidal anti-inflammatory drugs are avoided, and narcotics are used in the case of pregnancy. Follow-up should be done with a physical exam, blood work, and ultrasound.

Medical expulsive therapy can be used along with a trial of passage. Individuals with fever, infection, or obstetric problems are contraindicated for the trial of passage.

In such cases, intervention methods are indicated. Anatomical considerations like a solitary kidney or bilateral obstruction may require intervention for individuals with renal insufficiency. Other indications for intervention include refractory pain, nausea, vomiting, stone size greater than 1 cm, and nondiagnostic imaging.

If the procedure has to be performed on a pregnant woman, it requires experienced anesthesiologists, neonatologists, radiologists, urologists, and obstetricians.

Cardiopulmonary changes in pregnant women pose a complex management risk.

Temporary Drainage and Ureteroscopy

Since the last decade, definitive treatment has been accepted. Previously, the risks of surgery and treatment were considered very complex. Due to advancements in endourology, ureteroscopy has been developed and used. Even advancements in obstetrics have provided advantages.

Only some things are considered when choosing between temporary drainage and ureteroscopy. If infection and fever are present, ureteroscopy cannot be used, and temporary drainage must be performed. Sufficient resources should be present, like obstetric monitoring and lasers.

Other considerations for temporary drainage include

• Large stones.

• Complex anatomy.

• Bilateral stone disease.

• Obstetric complications.

• 1st-trimester presentation or presentation near full term.

• The preferences of the patient and surgeon should also be considered.

If only one choice is available, then it has many disadvantages. Temporary drainage has disadvantages. As this procedure is temporary, it may require definitive management at a later stage- postpartum. Additional procedures may be required during pregnancy due to physiological variations. This may cost more. Temporary drainage may not be tolerated well as there may be dislodgement of tubes, stents, migration, and colonization with bacteria causing urinary infection.

Advantages of temporary drainage include

• It can be done quickly.

• Minimal anesthesia is required.

• There is no exposure to radiation.

Because of the disadvantages of temporary drainage, definitive treatment with ureteroscopy is used.

Conclusion

Urolithiasis poses difficulties for pregnant women. It is very challenging to manage this condition among pregnant women. The exact decision to use the treatment options depends on the patient's condition. Hence, it is important to know about the condition in detail.