This document discusses the management of kidney stones during pregnancy. It notes that kidney stones are a common non-obstetric cause of hospitalization during pregnancy. While conservative management is preferred, around 1/3 of patients require surgical intervention due to uncontrolled pain or signs of obstruction/infection. Accepted surgical treatments include ureteral stenting, percutaneous nephrostomy drainage, and ureteroscopy during the second trimester. However, these options all carry risks of complications from repeated procedures or radiation exposure and are generally deferred until after delivery when possible.

1. NATURAL H/O STONE,MANAGEMENT OF STONES IN
PREGNANCY
DR. BIPUL THAKUR

2. EPIDEMIOLOGY
 Gender: men (2-3) >women
 RACE/ETHNICITY :- Whites, Hispanics, Asians , African Americans
 AGE:-Uncommon before age 20, peak incidence in the 4th to 6th decade.
 GEOGRAPHY:- higher prevalence in hot, arid, or dry climates such as the
mountains, desert, or tropical areas.
 CLIMATE :- Seasonal variation is likely related to temperature by way of fluid
losses from perspiration thus more in summer months.
 OCCUPATION:-Cooks, steel workers, workers at a glass plant.
 BODY MASS INDEX AND WEIGHT : Excrete more urinary oxalate, uric acid,
sodium and phosphorus along with increases supersaturation of Uric acid

3. Physiochemistry
 Stone formation is a complex cascade of events that occurs as the glomerular
filtrate traverses the nephron.
 It begins with urine that becomes supersaturated with respect to stone-forming
salts, such that dissolved ions or molecules precipitate and form crystals or nuclei.
 Once formed, crystals may flow out with the urine or become retained in the
kidney at anchoring sites that promote growth and aggregation, ultimately leading
to stone formation.

4. Inhibitors and Promoters of Stone
formation
 In urine, crystallization does not necessarily occur because of the presence of
inhibitors and other molecules.
 Inhibits crystal Growth
Citrate – complexes with Ca
Magnesium – complexes with oxalates
Pyrophosphate - complexes with Ca
Zinc
 Inhibits crystal Aggregation
Glycosaminoglycans
Urinary glycoproteins
-Nephrocalcin
-Tamm-Horsfall
-Uropontin/osteopontin
- Inter Alpha Trypsin

5. Promoters
 Bacterial Infection
 Matrix –(non-crystalline component )
 Anatomic Abnormalities – PUJ Obstruction , MSK
 Altered Ca and oxalate transport
 Prolonged immobilization: predisposes to Bone demineralization and
Hypercalciuria
 Increased uric acid levels i.e. taking increased purine subs– promotes
crystallization of Ca and oxalate .
 ?? Nanobacteria or Calcifying nanoparticles (CNPs )– seen in 97% of renal stone

6. Ryndall’s Plaque Hypothesis

7. Vascular Theory

8. Free particle Theory

9. Blocked Lymphatic Theory

10. Classification
 Calcium Stones 70-80%
– Ca Phosphate 5-10%
– Ca Oxalate/Phosphate 30-45% (Mixed)
– Ca Oxalate 20-30%
 Struvite stones 15-20%
 Cystine stones -3%
 Uric acid stones

11. Oxalate (Calcium)stones:
 Also Called Mulberry Stone
• Covered With Sharp Projections
• Sharp -Makes Kidney Bleed (Hematuria)
• Very Hard
• Radio – Opaque
• Under microscope looks like Hourglass or Dumbbell shape if monohydrate and
Like an Envelope if Dihydrate

12.  Hypercalciuria 3 types:
1. Absorptive: increased intestinal absorption of calcium
2. Renal: renal leak of calcium
3. Resorptive: increased demineralization of bone (due to hyperparathyroidism) ]
 Hypercalcaemia (primary hyperparathyroidism)
 Hyperoxaluria Due to:
1. Increased oxalate absorption in short bowel syndrome or malabsorption (enteric
hyperoxaluria)
 Hypocitraturia
 Hyperuricosuria (on the surface of which calcium oxalate crystals form).

13. Phosphate stones:
 Usually Calcium Phosphate
• Sometimes - Calcium Magnesium Ammonium Phosphate Or Triple Phosphate
• Smooth -Minimum Symptoms
• Dirty White
• Radio – Opaque
• Calcium Phosphate also called ‘Brushite’ appears like Needle shape under
microscope
• In Alkaline urine-Enlarges rapidly-Take the shape of Calyces- Staghorn

14. Renal tubular acidosis (RTA)
 defect of renal tubular H+ secretion resulting in impaired ability of the kidney to
acidify urine.
The urine is therefore of high pH, and the patient has a metabolic acidosis.
The high urine pH increases supersaturation of the urine with calcium and
phosphate, leading to their precipitation as stones.

15. Struvite stone
 form in persistently alkaline, ammonia-rich urine
 caused by the presence of urease splitting bacteria such as Proteus,
Pseudomonas, Klebsiella, Staphylococcus, or Mycoplasma species.
 Predisposing factors for struvite stones (commonly called infection stones) include
neurogenic bladder, foreign bodies, and recurrent UTIs.

16. Uric acid and Urate Stone
• Hard & Smooth
• Multiple
• Yellow or Red-brown
• Radio - Lucent (Use Ultrasound)
• Under microscope appear like irregular plates or rosettes

17.  Uric acid is essentially insoluble in acid urine and soluble in alkaline urine.
 Human urine is acidic and this combined with supersaturation of urine with
uric acid, predisposes to uric acid stone formation.
 20% of patients with gout have uric acid stones.
 Myeloproliferative disorders. Particularly following treatment with cytotoxic
drugs
 Idiopathic uric acid stone .

18. Cystine Stone
• Autosomal recessive disorder
• Usually in Young Girls
• Due To Cystinuria –
Cystine Not Absorbed by Tubules (Inherited Disease)
• Multiple
• Soft or Hard – can form stag-horns
• Pink or Yellow
• Radio-opaque
• Under microscope appears like hexagonal or benzene ring

21. INTRODUCTION
 Renal colic secondary to kidney stones is the leading non-obstetric cause for
hospitalization in the pregnant patient
 Incidence: 1:200 – 1:1500 pregnancies
 Increased risk for preterm delivery, preeclampsia, placenta previa, and preterm
premature rupture of membranes due to Renal colic, UTI and Urinary tract obstruction
 Multiparous: primiparous- 3:1, if adjusted for age: No significant difference
 Most patients with symptomatic calculi
present during the second or third trimester

22. Effect of Pregnancy on Urinary tract
 Dramatic changes of both anatomy and physiology of the upper urinary tract
 dilation of the renal calyces, pelvis, and ureters, usually evident by 6 to 10 weeks'
gestation -Most remarkable anatomical change
 Physiologic hydronephrosis is the most common cause of dilation of the urinary tract in
pregnancy and may produce pain that mimics renal colic from urolithiasis.
 Upper-tract dilation with a right-sided predominance is reported in up to 90% of pregnant
women by the third trimester and may persist up to 12 weeks postpartum

23.  Increased circulating progesterone during pregnancy causes ureteral smooth muscle
relaxation reducing the peristalsis
 Right>Left because of compression by engorged ovarian vein and uterine dextrorotation

24.  Elevated renal plasma flow and GFR increases filtered loads of Sodium, calcium and Uric
acid, causing Hypercalciuria and Hyperuricosuria
 Suppression of PTH and increased circulating 1-25 dihydrocholecalciferol production by
Placenta – increases intestinal absorption of calcium
 Hypercalciuria in Alkaline urine pH- crystallization of calcium phosphate

25. FETAL CONSIDERATIONS
 Radiation Exposure • human body absorbs almost 90% of the exposed diagnostic
radiation • the radiation dose absorbed (amount of energy deposited in the tissue
by radiation) by a person is measured using the unit Rad or Gray (Gy).
 Potential effects of irradiation on the fetus include teratogenesis , carcinogenesis,
and mutagenesis
 During the first trimester, the period of early organogenesis and rapid cell division,
the embryo is highly sensitive to the effects of radiation

26. Principal effects
 The effects : nonstochastic or stochastic.
 Nonstochastic effects - cumulative with increasing dose and for which a threshold (< 50
mGy are considered as safe) is believed to exist. Eg; malformation, growth retardation, and
cataract formation (teratogenic)
 Stochastic effects - probability of the effect gets worse with increasing dose and where
there appears to be no threshold. Eg; the risk of malignancy and genetic effects.
 (Carcinogenesis- dose even < 10 mGy present a risk and mutagenesis - 500-1000 mGy
doses are required)

27.  radiation >0.5 Gy represents a major risk to the embryo •
 The risk is critically dependent on - gestational age and the total amount of radiation
delivered
 Exposure to fetus: X ray KUB - 0.5 mGy , standard IVU - 3 mGy and a limited IVU - 2 mGy

30. Clinical features
 Flank pain
 Macroscopic or microscopic hematuria
 LUTS
 A diagnosis of urinary calculi should be considered in evaluation of a pregnant patient who
suffers from persistent infection with urea splitting organism
 microscopic hematuria reported in up to 75% of cases and gross hematuria in up to 15%
of cases • Bladder stones are reportedly rare during pregnancy

32. Imaging modalities
 USG:
Initial diagnostic modality of choice
difficult to adequately visualize the ureter or distinguish physiologic hydronephrosis
of pregnancy from ureteral obstruction because of calculus
sensitivity- 34%, specificity: 86%
 ureteric dilatation below the pelvic brim is highly suggestive of pathological distal
ureteric obstruction

33. MRU
 does not visualize calcium, stones are visualized as filling defects overlying the
high signal intensity of urine.
 Elucidation of smaller stones with this technique is difficult In symptomatic patients,
MRI has been reported to accurately differentiate physiologic hydronephrosis of
pregnancy from hydronephrosis resulting from an obstructing ureteral calculus
 MRI protocols for pregnant pts - rapid acquisition with relaxation enhancement
(RARE) (Sn-100%), fast spin-echo (FSE), and half-Fourier acquisition single-shot
turbo spinecho (HASTE)

34. IVU
 difficulty in differentiating delayed excretion of the contrast associated with physiological
dilation from that associated with obstruction due to calculus
 enlarged uterus and fetal skeleton may obscure small stones.
 Depression of fetal thyroid function is a potential side effect ( free iodide )
 exposure to contra media should be avoided.

36. CT SCAN
 radiation exposure via CT scan is at a dose much lower than the exposure
associated with fetal harm.
 Utilization of low-dose radiation exposure CT has emerged as a technique of high
utility and low risk for the pregnant patient and fetus
 low-dose CT can be defined as <3.5 mSv, and ultra-low dose as <1.9 mSv
 safe in pregnancy from the non-stochastic teratogenic standpoint, but not
stochastic effects including delayed hematologic malignancy.

37. Trans vaginal Ultrasound
 Imaging of Distal Ureter

38. MANAGEMENT
CONSERVATIVE:
 70%–80% of pregnant patients with symptomatic calculi will pass them
spontaneously with hydration, analgesia
 Indications for a more aggressive approach:
(1) obstruction of a solitary kidney
(2) sepsis
(3) colic refractory to drug therapy

39.  NSAID prostaglandin synthesis - premature closure of the ductus arteriosus in utero and,
therefore, should be avoided
 preferred analgesic regime has been frequent, small doses of morphine
 morphine on chronic use - fetal narcotic addiction, intrauterine growth retardation, and
premature labor. •
 codeine is teratogenic when used in the first trimester
 Antibiotics of choice – penicillins, cephalosporins, Erythromycin

40.  Tamsulosin nifedipine - used off label, but not FDA approved for use in pregnancy
 smooth muscle relaxation benefit may prove less useful in pregnancy, as the ureters are
already physiologically dilated.
 Tamsulosin is classified as a category B (defined as no demonstrated risk in animal
reproduction studies, but lacking adequate studies in pregnant women) • ? sudden infant
death syndrome (SIDS) with Tamsulosin.

41.  Premature labor from renal colic is the most common obstetric complication of
urolithiasis.
 Standard tocolytic therapy with beta adrenergic agents halts premature labor
 single dose of terbutaline sulfate 0.25 mg iv/sc arrests contractions
 risk of premature labor should cease completely with the passage or removal of the stone

42. SURGICAL TREATMENT
 Required in 1/3rd of patients due to pain uncontrolled by analgesia or signs of
persistent obstruction and infection.
 Management options:
Ureteral stent placement
PCN Drainage
URS

43. URETERAL STENT PLACEMENT
 Although ureteral stents effectively drain an obstructed collecting system, they are
by no means the perfect solution to this problem.
 Changes in Urine chemistry during pregnancy, Hypercalciuria and Hyperuricosuria
leads to accelerated encrustation of ureteral stent
 Needs stent exchange every 4-6 weeks
 In early gestation, require multiple stent changes – predisposes to bacteriuria, UTI
and stent migration leading to serious adverse effects on pregnancy
 Ureteral stents themselves are associated with pain, which can have a negative
effect on a patient's quality of life.

44. Percutaneous Nephrostomy
 alternative treatment option for pregnant patients with obstructing renal calculi
 effectively drain an obstructed collecting system.
 Limitations:
1.encrustation
2.colonization
3.pain
4.dislodgement
5.need for multiple interventions

45.  In an analysis of 29 pregnant women managed with nephrostomy drainage, over
one-half required tube exchanges, replacements, or flushing because of either
dislodgement or obstruction (Khoo etal., 2004).
 Indeed, the majority of pregnant patients managed with nephrostomy drainage
required exchange of the tube because of occlusion from debris(Kavoussi et al.,
1992).
 One-third of the patients in this series ultimately required nephrostomy removal
because of recurrent drain obstruction, fever, or pain.
 Ultimately they require Definitive management in Postpartum period for stone
removal.

47. Ureteroscopy
 Diagnostic and therapeutic
 Overall complications are uncommon
 Contraindications:
(1) stone size > 1 cm
(2) multiple calculi
(3) a solitary kidney
(4) sepsis
 uretroscopy is best performed in 2nd trimester.
 Most distal ureteric stones can be retrieved with a stone basket
 Fragmentation can be accomplished safely with pulse-dye laser, holmium:YAG
laser or pneumatic lithotripsy •
 Use of low dosed and pulsed fluoroscopy combined with lead shielding of the
patient’s pelvis can reduce total radiation exposure

48.  Although there have been reports of the inadvertent treatment of pregnant patients
with shock wave lithotripsy, with no adverse sequelae to the fetus, pregnancy
remains a contraindication to this treatment modality (Chaussy and Fuchs, 1989;
Frankenschmidt and Sommerkamp, 1998).
 Highly invasive therapies like PCNL is deferred until after delivery because of
prolonged anesthesia and radiation exposure

49. Asymptomatic stones in Patients contemplating Pregnancy
 renal stones tend to become symptomatic during pregnancy.
 Therefore, the management of asymptomatic calculi in women of childbearing age
must be considered in order to avoid the risks of subsequent management during a
pregnancy
 recurrent gross hematuria, documented stone growth, UTI, and recurrent renal
colic associated with a mobile calyceal stone are all indications for prophylactic
treatment in women of childbearing age

51. Reference
Campbell walsh wein Urology-12th Edition