Review for 10.1186/1471-230X-2-15 (2002)

Reviewer's report
 Bouveret's Syndrome Complicated by Distal Gallstone Ileus after Laser Lithotropsy Using Title:
Holmium: YAG Laser
Authors:
Mohammad M. Alsolaiman (modar9@hotmail.com )
Christoph Reitz (luckyluko@mindspring.com )
Ali T. Nawras (nawrasa@mail.amc.edu )
John B Rodgers (RodgerJ@mail.amc.edu )
Benedict J Maliakkal (MaliaKB@mail.amc.edu )
 1  14 May 2002 Version: Date:
 Dr Joel Teichman Reviewer:
 A paper of considerable general medical or scientific interest Level of interest:
 Accept after discretionary revisions Advice on publication:
This paper details an unusual case report of Bouveret's syndrome after holmium:YAG lithotripsy of large
gallstone in the duodenum. Several issues are raised by this case, and I think any surgeon who uses 
the holmium:YAG laser would benefit from the authors' experience. 
Compulsory Revisions: 
1) What endoscope was used (size and working channel size)? In urologic applications, calculi as large 
as 3 cm can be ablated within 2-3 hours using the smaller optical fibers (272 um or 365 um). If a 
sufficient working channel is available, a 550 um fiber where the beam exits at a 70 degree angle provides more efficient (i.e., faster) lithotripsy than an end-firing optical fiber (J Urol 1998; 159: 
690-694). Bladder calculi up to 6 cm can generally be ablated using a side-firing fiber under an hour 
(Urology 1997; 50: 44-48). It is also important that the holmium:YAG laser be used with the optical fiber 
tip in contact with the stone, as any separation distance reduces laser fluence and lithotripsy speed (J Urol 1998; 160: 471-476). 
2) What laser pulse energy and rate settings were employed? Generally, the most efficient lithotripsy 
occurs for most calculus compositions at a pulse energy of 1.0 J at 10 Hz (J Urol 1998; 160: 471-476, J 
Endourol 1999; 13: 559-566). 
3) Was fluid irrigant used? If so, was fluid irrigated by gravity or by a hand pumping device? As the 
authors indicate, no cracking was observed. Holmium:YAG fragments stones by a photothermal mechanism (J Endourol 1999; 13: 181-190). This process seems to "resect" the stone in small pieces 
rather than the "cracks" induced by short pulse duration lasers which induce photoacoustic effects 
(Lasers Surg Med 1995; 16: 134-146). As a result of the photothermal mechanism, holmium:YAG produces tiny debris of all calculus compositions (J Urol 1998; 159: 18-27). Endoscopically, the plume of small fragments looks like a "snowstorm" which obscures endoscopic vision-- we find that use of a 
hand pumping device for irrigation clears the debris and allows for continued laser lithotripsy under 
excellent vision. Further, the tiny craters created translates to a slow fragmentation process as the 
authors indicate. 
Discretionary comments: 
1) In retrospect, it is obvious that the lithotripsy debulked the stone to allow it to disimpact, and then 
migrate distally in the ileum. Why did the authors stop their procedures? Again, knowing that 
holmium:YAG lithotripsy produces tiny fragments and a slow stone "resection" leads us to approach large stones with the intent to debulk stones in planes, in order to divide the stone into pieces, which can then be retrieved with a basket or forceps.
Competing interests:
None declared.