Introductory Chapter: Complicated Urolithiasis

1. Introduction

Urolithiasis management is simplified with the introduction of shock wave lithotripsy (SWL), in the 1980s, with the help of technological advances in endourology in the last quarter of the century. Stones are said to be “complicated” when they are associated with conditions which impact diagnosis and management. Stones in anomalous kidneys, stones following urinary diversion, stones formed/identified during pregnancy and stones in calyceal diverticulum are all considered to be complicated stones.

2. Kidney stones in pregnancy

The incidence of urolithiasis is increasing around the world. Urolithiasis is more common among men; however, the prevalence among women is increasing [1]. Around 7.1% women in the USA suffer from nephrolithiasis, and the incidence is on the rise [2]. Renal colic secondary to a kidney stone is the most common nonobstetric hospital admission diagnosis for pregnant women. The incidence of a symptomatic stones varies from 1 out of every 200–1500 pregnancies. Kidney stones in pregnancy are associated with significant complications including preterm labor and even delivery, premature rupture of the membranes, pregnancy loss, gestational hypertension which can lead to pre-eclampsia and urinary tract infections [3].

Women during pregnancy are more likely to form stones than otherwise [4]. Increased incidences of stones during pregnancy are often related to urinary stasis and collecting system dilation. It is a consequence of ureteral compression due to gravid uterus and progesterone-induced ureteral dilation. Besides anatomical factors, there are many biochemical changes favoring development of kidney stones. These include hypercalciuria and high urinary pH [5]. Imaging is not always successful in differentiating between obstruction and physiology. Majority of the stones are hydroxyapatite, mostly isolated and unilateral. The most common variety of stones formed during pregnancy is calcium phosphate (hydroxyapatite) [6]. The preponderance of hydroxyapatite stones is unclear; however, the probable cause is the pregnancy-related physiological alterations including increased calcium excretion and high urinary pH. The tendency to form stones continue to persist even after the pregnancy, during pregnancy second and third trimester and lasting until about 3 months following delivery [3].

Imaging is the cornerstone of diagnosis like in the nonpregnant population. Understandably ultrasound is the most frequently performed imaging. In various series, sensitivity of ultrasound in the detection of urolithiasis is highly variable. The reported sensitivity of ultrasound during pregnancy varies from 29 to 95% [7]. Ultrasound could be falsely negative in over two-third of the cases, as it relies mostly on secondary signs. Visualization of stones in the ureter is often difficult due to the gravid uterus and it relies on secondary signs, that is, hydroureter. Ureteral dilation during pregnancy is often due to a gravid uterus in over 90% of cases. The intrarenal resistive index (RI) estimation is an additional parameter that can improve the ability to differentiate obstruction from physiologic hydronephrosis. Mean value of 0.7 (45% sensitivity and 91% specificity) and difference between the two units of 0.06 (95% sensitivity and 100% specificity) is indicative of obstruction [8]. The other important Doppler ultrasound parameter frequently employed is the ureteral jet phenomenon. Both absence of ureteral jet and an elevated RI improves ultrasound’s ability to diagnose obstruction from 56 to 72%. Transvaginal ultrasound is another important tool in the detection of distal ureteral stones [9]. In a study, it was observed that compared to transabdominal ultrasound, transvaginal ultrasound improves the ability to diagnose distal ureteral stones by threefold. The combination of transabdominal and transvaginal ultrasounds improve the ability to diagnose distal ureteral stones in 85% of the cases.

MRI scan is the second-line imaging if ultrasound fails to provide definitive answers. Both the AUA and EAU guidelines support this recommendation [7]. Noncontrast MR scans versus gadolinium enhanced studies (MR Urography) is still a contentious issue. However, American College of Obstetrics and gynecology (ACOG) recommends use of gadolinium contrast for scenarios where the benefit clearly outweighs the potential risks [10]. MRU without contrast (Single-shot turbo-spin echo) is reported to be 89% accurate in differentiating physiological hydronephrosis from obstruction secondary to urolithiasis. The overall positive predictive value of MR for ureteral stone is reported to be around 80% [11].

Noncontrast enhanced CT (CTKUB) is the gold standard in the evaluation of suspected uretero renal colic secondary to stone in both adult male and nonpregnant females and in children. However, radiation-induced nonstochastic (teratogenesis) or stochastic (carcinogenesis, mutagenesis) effects are a major concern. As a general principle, any imaging investigation resulting in an absorbed dose to the fetus of >0.5 mGy requires justification [11]. The teratogenic effects of fetal radiation exposure are cumulative with increasing dose. Potential fetal abnormalities include growth retardation, severe mental retardation, and microcephaly. Even the pregnancy loss can happen. The risk of fetal abnormalities is negligible at levels below 50 mSv. First two months of pregnancy and after 23rd week are safer periods. Current CT protocols particularly with low dose (<4 mSv) and ultralow dose CT (<1 mSv) are even safer. The current EAU guidelines recommend that ultrasound should be the preferred mode of imaging in pregnant women; MRI be used as second-line imaging and use low dose CT as a last option.

The contemporary management of acute kidney pain during pregnancy is by hydration, use of anti-emetics, and adequate pain control. Acetaminophen and if needed narcotics are safe for pain management. Spontaneous passage of stones is observed in 23-84% of cases [12]. Due to altered cell mediated immunity, up to 17% of women admitted with urolithiasis have accompanying pyelonephritis. Febrile infections secondary to obstructive uropathy are often observed due to altered cell mediated immunity. One in six women admitted for urolithiasis have pyelonephritis. Management is difficult due to limited choice in the use of medications. NSAIDs and codeine-containing medications for pain and fever and among antibiotics including penicillin, cephalosporins, and erythromycin are safer. Aminoglycosides, tetracycline, chloramphenicol, fluoroquinolones, and sulfa antibiotics, however, are contra-indicated. Medical expulsive therapy use is ‘off label’ and belong to category B [13]. Interventional treatment is needed in about one in four to one in three pregnant women. Intervention is often indicated in cases of intractable pain, severe or progressive hydronephrosis, bilateral obstruction, or obstruction in a single functioning kidney, urosepsis secondary to obstructive uropathy. Women who develop obstetric complications like preterm labor or preeclampsia constitute failure of conservative treatment and mandate active intervention. Diversion using percutaneous nephrostomy (PCN) or insertion of double J stents are the most frequently performed [14]. There are pros and cons of both, whereas PCN is a shorter procedure under local anesthesia, it also facilitates subsequent PCNL (Figure 1) and is better in septic conditions, double J stents facilitates subsequent ureteroscopy, but often require a replacement in a matter of weeks to months due to higher incidence of encrustation and often require spinal anesthesia [15]. Ureteroscopy during pregnancy is associated with high success rates and should ideally be performed in the second trimester under either local or spinal anesthesia subject to ultrasound guidance. Fluoroscopy and general anesthesia should be avoided, particularly in the last trimester. PCNL and ESWL are associated with very high complication rates and should be avoided. ESWL is associated with miscarriage, congenital malformation, intrauterine growth retardation, placental disruption, and fetal demise [16], and therefore should not be performed.

Figure 1.

A 27-year lady, 24 weeks pregnant presented to the emergency room with intractable pain, vomiting, and fever. Conservative management failed. Her ultrasound (A) showed hydrocalicosis and renal pelvic stone 15 mm. In view of failure of conservative treatment, a PCN was placed (B) and subsequent ultrasound (C) showed resolution of hydronephrosis, stone (arrow) and PCN. Postpartum CT (D) confirmed the presence of stone, and she underwent an unremarkable mPCNL.

In essence, urolithiasis during pregnancy is a challenge in both diagnosis and its management. Managing complex urolithiasis particularly with sepsis must be managed in a multidisciplinary setting with the active involvement of an obstetrician, radiologist, and urologist [17].

3. Urolithiasis in urinary diversions

Removal of the urinary bladder for muscle invasive bladder cancer, requires urinary diversion. Urolithiasis following urinary diversion is a relatively frequent complication. Diversion increases the risk of urolithiasis due to anatomical factors such as kidney dysfunction and stasis, recurrent infections, metabolic abnormalities, and presence of foreign bodies, including mucous and exposed staple lines [18]. Stones can form in both the upper and lower urinary tract. In a series of over 1000 cystectomies and ileal conduit urinary diversion with a mean follow-up of 75 months, upper-tract urolithiasis was observed in 13.4%, whereas 4.5% developed stones in the conduit [19]. Similarly, stones are also formed in the reservoir as well in the upper tract in orthotopic neobladder formation. It is more frequently observed in stapled anastomosis compared to hand sewn [20].

Multiple factors play a role in increased incidence of urolithiasis with a urinary diversion. Metabolic abnormalities are more frequently observed following continent and orthotopic neobladder. Hyperchloremic metabolic acidosis, hypercalciuria, hyperoxaluria, and hypocitraturia are some common metabolic abnormalities in this cohort. The other changes like bone loss, recurrent infections, and development of CKD due to recurrent infections are major reasons for urinary hypercrystallization with stone formation. A cohort of 77 patients reported to have developed urolithiasis over 7 years of follow-up, Herzig et al. [21] noted that the most common stone composition was MAP stones in 63.5%, calcium phosphate stone in 25%, and only 11.5% were calcium oxalate stones (9.6% Wavellite and 1.9% Weddellite). Persistence of asymptomatic bacteriuria and urinary stasis following treatment of stones and infection results in high recurrence rate. Structural factors include presence of foreign bodies, urinary stasis, and mucus plugs providing nidus for recurrent urolithiasis. Foreign bodies include nonabsorbable sutures and staples, stents, and indwelling catheters. Urinary stasis results from inadequate emptying due to mucus and hypercontinence, uretero-intestinal anastomosis strictures, ureteric transposition (left-sided stones more common) [22], and stomal stenosis [23].

Interventional management of the stones involves flexible ureteroscopy (fURS) or combined ante and retrograde approaches, the rendezvous procedures. System is often dilated secondary to stones or obstruction; however, for nondilated systems, it is important to prestent the affected renal unit with an antegrade percutaneous tube (PCN) as well. This is needed for most complex stones and for easy maneuvering of the flexible instruments through difficult anatomy. For a nondilated system, ultrasound-guided puncturing on the stone, retrograde contrast study by placing a Foley’s catheter with an inflated balloon and pushing contrast into the conduit for retrograde filling of the system is needed. If everything else fails, trauma protocol on table IVU with 2 mL of intravenous contrast may provide enough opacification for calyceal puncture. A careful inspection of the reservoir is important as foreign bodies (staples, sutures, etc.), stents mucus plugs forms a nidus for future recurrence. Most important is to achieve complete stone clearance and do medical treatment postoperatively to decrease recurrence. Infective stones are notoriously recurrent; therefore, 6–12 weeks of antibiotics are often recommended. For strictures and stenosis balloon dilation, stenting is recommended, and in certain situations, surgical revision of the uretero-intestinal anastomosis is recommended (Figure 2).

Figure 2.

A 68 years old had a radical cystectomy and orthotopic neobladder in 2015 for muscle invasive bladder cancer. He presented with left flank pain and hematuria 7 years after the surgery, work up indicated hydronephrosis (arrow a, c) right distal ureteral stone (a, d) slightly proximal to the uretero-ileal anastomosis. He was initially managed by oral dissolution therapy (potassium citrate) and medical expulsive treatment. Conservative treatment failed and was subsequently treated by rendezvous procedure with antegrade and retrograde flexible ureteroscopy.

4. Urolithiasis in anomalous kidneys

The incidence of urolithiasis is higher in kidneys with anomalies of fusion, lie, or rotation [24].

Urolithiasis in anomalous kidneys pose special challenge due to differences in the lie rotation, and orientation of the calyces compared to an orthotropic kidney. Most common anomalous renal abnormalities include horseshoe kidney, ectopic pelvic kidney, and malrotated kidneys. Horseshoe kidney is the commonest of abnormalities. The anatomical anomaly causes fusion of lower pole which results in the abnormal position of UPJ, a high-placed UPJ, and malrotation and anterior displacement of the collecting system [25]. Preoperative work up should be meticulous to identify anatomical variations. CT urogram is often the study of choice. However, innovative meticulous planning uses artificial intelligence (AI) and 3D [26].

SWL, since its inception, due its non-invasive nature, became the treatment of choice. It is not suitable for most Kidney stones in anomalous kidneys due to location and even when appropriate, it is often associated with significant residual fragmentation and poor clearance. The stone clearance is reported to be under 70% in larger reported studies [14]. In a well-equipped endourology center, SWL is not the first choice in most anomalous kidney stones (Table 1).

Renal anomaly	Incidence	Anatomical variations
Horseshoe kidney	1 in 400 (live birth)	Abnormally placed UPJ; High UPJ; Anterior and malrotated calyx
Ectopic kidney	1 in 1000 (live birth)	Location and relationship with surrounding organs
Malrotated kidney	1 in 2000 (autopsy)	Variable orientation of renal pelvis, collecting system, and renal vessels
Calyceal diverticulum	Rare	Outpouchings from the collecting system, epithelial lining, muscular layer, and narrow channel

Table 1.

Renal anomalies, incidence, and anatomical variations causing urolithiasis.

UPJ = Ureteropelvic junction.

Lim et al. [27] performed an interesting global study on the propensity score-matched pair analysis on data collected from 20 centers with urolithiasis in anomalous kidneys, Being treated with retrograde intrarenal surgery (RIRS) or mini PCNL (mPCNL). The treatment decision was made by the operating surgeon according to his preference and expertise. Authors concluded that both mPCNL and RIRS are safe and efficacious with mPCNL, demonstrating a higher stone free rate. Stones in anomalous kidneys are a complex medical condition and require expertise and availability of most endourological armamentarium. The treatment must be tailored according to individual needs of the patient. In patients with moderate-to-high stone burden, ectopic kidney’s access to both RIRS and mPCNL is important. Endoscopic combined intra renal surgery (ECIRS) Often provides the necessary access to right calyx and do directed treatment (Table 2).

Renal anomaly	mPCNL	RIRS	ECIRS	SWL
Horseshoe kidney	+++	++	+++	+
Ectopic kidney	+	+++	+	—
Malrotated kidney	+++ (for stones >2 cm)	+++ (for stones ≤2 cm)	+++	+
Calyceal diverticulum	++	++	+++	—

Table 2.

Pros and cons of various treatment options in renal anomalies with urolithiasis.

Level of recommendation = +; mPCNL = mini percutaneous nephrolithotomy; RIRS = Retrograde intrarenal surgery; SWL = Shock wave lithotripsy.

One of the major concerns when performing mPCNL on anomalous kidneys is the risk of bleeding. In a recent paper, Feng et al. [28] observed that Tranexamic acid may be a useful adjunct to prevent major bleeding. Technological developments in flexible ureteroscopy have made the RIRS as a first choice for most small-to-moderate size stones in the anomalous kidney. It is also indicated in situations where either SWL or mPCNL is not feasible or has failed (Figure 3).

Figure 3.

A 29-year-old known case of urolithiasis, presented with acute colic imaging indicated 16 mm proximal ureteral stones and multiple small kidney stones (imaging not shown). Underwent RIRS and stenting. Stent removed after 2 months and was considered for ESWL for residual stones, however due to significant stone burden PCNL was advised. A renal vein (white arrow); B renal artery (white arrow) and C. malrotation and stones in renal pelvis and calyces.

5. Conclusions

Pregnancy is an independent risk factor for urolithiasis. In endemic areas, women with a history of urolithiasis, should undergo basic work to exclude kidney stones before planning pregnancy. Management of stones during pregnancy is complicated and compromised, particularly in the first and last trimester. Radiations should be avoided in the first trimester and interventions only when necessary.

Stones in urinary diversions are frequently seen. Stones can form as early as first year following diversion, so monitoring is important. Medical treatment is required after interventional treatment to avoid recurrence. Infection and obstruction are the two significant risk factors; infections are invariably present so perioperative antibiotics should be used. Most patients have hydronephrosis at presentation, so a PCN is always handy to have subsequent endourological interventions. CT is necessary to understand the anatomy, and loopogram is also helpful.

Stones in anomalous kidneys pose a challenging situation and require precise delineation of anatomy using a CT urogram. It helps to clarify calyceal and vascular anatomy. SWL is often not effective due to stone clearance issues [29]. PCNL and RIRS are the options of choice. RIRS is now considered the gold standard for most small-to-moderate size stone; ECIRS is an optional approach to malpositioned (ectopic) that often require laparoscopic guidance to PCNL; however, RIRS is a safer option.