Kelly C. et al., 2019: Nephrolithiasis in the Obese Patient
Kelly C, Geraghty RM, Somani BK.
University of Southampton, Southampton, UK.
Department of Urology, University Hospital Southampton, Tremona Road, Southampton, SO16 6YD, UK.
PURPOSE OF REVIEW: The link between metabolic syndrome (MetS)/obesity and kidney stone disease (KSD) has gained importance over recent years due to the increasing prevalence and healthcare burden worldwide. This review analyses the literature exploring the link between MetS/obesity and KSD and the impact that obesity has on KSD management. RECENT FINDINGS: Metabolic syndrome has been shown to increase an individual's risk of developing kidney stone disease, with insulin resistance forming a core component of the pathophysiology. The body habitus of an individual also influences the type of intervention that is most appropriate, with flexible ureteroscopy increasingly being the preferred option in obese patients. It is important for urologists to consider the features of metabolic syndrome to effectively manage episodes of KSD in obese patients. In addition, better quality evidence is required to effectively compare different treatment options in this group of patients.
Curr Urol Rep. 2019 May 18;20(7):36. doi: 10.1007/s11934-019-0898-0. Review
Treatment of stone disease in obese patients is a clinical challenge both surgically and medically. The increased risk of stone formation associated with the metabolic syndrome indicates that stone removal will be required in an increasing number of obese patients.
For this group of patients it is necessary with both medical and technical considerations.
One of the limitations of the use of SWL is the long skin-to-stone distance that in patients with high BMI even might exceed not only the recommended distance for treatment, but also the maximal geometrical penetration depth of the lithotripter.
The associated loss of shockwave energy contributes to the sometimes poor disintegration. Although the latter obstacle occasionally can be compensated for by increased shockwave power, the higher risk of subcapsular renal hematoma is another problem that needs attention. Moreover, patients with metabolic syndrome also very often have hypertension that needs to be noted.
For the reasons mentioned, RIRS is recommended as first line treatment and comparative studies referred to in this article not unexpectedly resulted in a higher stone-free rate. Similar results were recorded with PCNL.
But a remaining problem is that obese patients generally have a high morbidity with increased anaesthetic risk. The final decision for the most appropriate treatment therefore needs to be balanced against the different problems discussed above.
Reviewer’s reflection: I have personally with relatively good results treated several severely obese patients just because other treatment alternatives actually were excluded attributable to the high risk level.
The problem with “radiolucent” stones can easily be avoided because the vast majority of those stones are composed of uric acid. These patients normally do not need surgery but can successfully be treated with oral chemolysis.
The bottom-line is that although obese patients require active stone removal, great care is necessary for selecting the most appropriate treatment and SWL is one important tool to consider in this process.
Addition: For urologists who are uncertain of the definition of metabolic syndrome the following information extracted from the article might be helpful with variables expressed in SI-units: