Assessing Urinary Tract Junction Obstruction Defects by Methylene Blue Dye Injection

Summary

Methylene blue dye injection into the renal pelvis facilitates the assessment of urinary tract junction obstruction defects during mouse embryonic urinary tract development. Here, a protocol for methylene blue dye injection into the renal pelvis is described.

Abstract

Urinary tract junction obstruction defects are congenital anomalies inducing hydronephrosis and hydroureter. Murine urinary tract junction obstruction defects can be assessed by tracking methylene blue dye flow within the urinary system. Methylene blue dye is injected into the renal pelvis of perinatal embryonic kidneys and dye flow is monitored from the renal pelvis of the kidney through the ureter and into the bladder lumen after applying hydrostatic pressure. Dye accumulation will be evident in the bladder lumen of the normal perinatal urinary tract, but will be constrained between the renal pelvis and the end point of an abnormal ureter, if urinary tract obstructions occur. This method facilitates the confirmation of urinary tract junction obstructions and visualization of hydronephrosis and hydroureter. This manuscript describes a protocol for methylene blue dye injection into the renal pelvis to confirm urinary tract junction obstructions.

Introduction

The urinary system consists of a pair of kidneys and ureters and a common bladder and urethra. The main function of the urinary system is to maintain body homeostasis by managing the water and electrolyte balance of the blood. The kidneys filter the blood to control electrolyte concentrations and acid-base balance,and produce urine to excrete excess water and waste including solutes and metabolites. Urine is then transported through the ureter from the renal pelvis of the kidney to the bladderin a unidirectional manner where it is stored and ultimately eliminated via the urethra¹.

The ureters are straight tubes origi....

Protocol

Mice (Wnt5a flox/flox mice (Wnt5a^tm1.1Tpy) and Dll1Cre line, UVJO mouse model)⁷ were managed according to NIH guidelines for the care and use of laboratory animals and studied under a protocol approved by the NCI-Frederick Animal Care and Use Committee.

1. Preparation of Methylene Blue Dye Solution

1. Measure 0.1 g methylene blue powder.
2. Dissolve the methylene blue in 10 mL normal saline or 1x phosphate buffered saline (PBS) completely by vortexing.
3. Filter the 10 mg/mL methylene blue solution with a syringe filter (membrane pore size 0.45µm) to e....

Results

The kidneys and lower urinary system are located dorsal to most other internal organs such as the liver and intestine. After removing these other internal organs, a pair of kidneys and ureters and a single bladder are visible (Figure 1A). Upon successful dissection, the dye injected into the renal pelvis will flow from the kidney into the bladder via the ureter. The renal pelvis is the funnel-like dilated proximal part of the ureter in the kidney. Therefore, .......

Discussion

Mouse kidneys are functional beginning at E16.5 and a dye injection test is theoretically possible from this time point. However, the kidney is too small to be injected with the dye solution and phenotypes such as hydronephrosis and hydroureter are not clearly observed since these phenotypes are a secondary effect of urine built up due to abnormal urine transport. These phenotypes, from the obstructions such as UPJO or UVJO, are evident at E18.5 by distended kidneys and ureters. Larger kidneys of embryos at E19.5 or neon.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Methylene blue	Sigma-Aldrich	M9140
Quality Biological Inc. NORMAL SALINE - 500ML	Fisherscientific	50-983-204
3 mL disposable syringe with BD Luer-Lok tip	BD	309657
Acrodisc Syringe Filters with Supor Membrane	Pall corporation	4614
Exel Scalp Vein (Butterfly) Sets; 27G x 3/4" 12"	EXELINT	26709
Delicate Operating Scissors	Roboz Surgical Instrument Co.	RS-6702
Micro Dissecting Forceps	Roboz Surgical Instrument Co.	RS-5135
Dumont Tweezers; Pattern #5	Roboz Surgical Instrument Co.	RS-5045
BD PrecisionGlide Needles 30 G x 1/2"	BD	305106