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Author: Dr. Suneet Sood
Editor: Dr. Suneet Sood
Narrators: Thong Yi Kun, Alan Koay, Siah Tse Nin

Transcript

Dr Jagdip was speaking. Lecturing, really, I thought, trying to fight boredom.

There were six of us in the urology ward, discussing a patient with a varicocele. I stole a glance at Perminder, standing to my left. Perminder was all attention, as usual. And now he had started to wring his hand, a sure sign that he was upset because something Dr Jagdip was saying didn’t make sense to Perminder. Perminder, the class genius, always got upset when things didn’t make sense.

“…so we ligate the testicular veins in order to treat a varicocele,” Dr Jagdip was saying. “This is called Palomo’s operation. Something on your mind, Perminder?”  She, too, noticed Perminder’s agitation.

“Er, well, you just told us that a retroperitoneal tumor or a left renal tumor can cause varicocele by blocking off the testicular vein…”

“Yes, I did. On the left side, the testicular vein enters the renal. A renal tumor can grow and block off the testicular vein, resulting in a varicocele. In fact, a recent left-sided varicocele in a 40+ male should make you think of renal tumor.”

“But, if obstruction of the testicular vein causes varicocele, why should surgical ligation of the testicular vein result in curing a varicocele?”

“Well, Well, that’s the way medicine is. It works. Everything doesn’t always make sense.” Dr Jagdip faltered. Clearly she hadn’t thought of this.

We were all amused, as were some of the other students, but we didn’t smirk for too long. Dr Jagdip was quite a nice person, actually, even though she was a little dull. As she finished teaching, she asked a last question.

“Why is a varicocele more common on the left side?”

I answered. I had read it in the surgery book last night.

“It’s because the left testicular vein enters the left renal at a right angle, while the right testicular vein enters the vena cava at an obtuse angle. These hemodynamics favor higher left-sided pressures, which predispose patients to left-sided varicoceles.”

I had impressed Dr Jagdip. In fact, I had impressed myself: I had been able to quote the book verbatim.

But Perminder was wringing his hands again. Only this time he remained silent.

As soon as the class finished, I asked him, “What?”

“What what” asked Perminder.

“You didn’t agree with that answer about why left-sided varicoceles are more prevalent.”

“No, I didn’t. Your answer was wrong.”

“But that’s what the book says.”

“I know” said Perminder. “But the book is wrong.”

I knew better than to scoff. Perminder was Perminder. “So tell me.”

“The angle makes no difference. The pressures are transmitted in accordance with the laws of physics, and are transmitted very well across angles. The real reason for the increased frequency of left-sided varicoceles is that the pressure in the left renal vein is much higher than that in the vena cava. The left testicular vein drains into a high-pressure system. The right drains into a low-pressure system.”

“But why is the pressure in the renal vein so high? It drains blood only from the kidney! And the IVC carries much more blood.”

“That’s true, but the IVC is wider than the renal vein. Therefore the pressure in the renal vein is higher than the IVC. Remember Poiseuille’s law? Pressure is inversely proportional to the fourth power of the radius? So even a small decrease in radius causes a marked increase in the pressure within the renal vein.”

“Hm,” I said. That makes a lot more sense than the right angle theory.

The next day Perminder said, “I’ve worked out the Palomo-tumor contradiction.”

“Which one?” I asked. I had already forgotten yesterday’s class.

“Why a tumor can block the left testicular vein and cause varicocele, and yet a ligation of the testicular vein can cure it.”

“Oh that one!” I said. Now I was interested. “Tell.”

“Let’s first talk about a tumor. When a tumor blocks the testicular vein, the vein and its tributaries will dilate. That’s to be expected. The blood from the testes has nowhere to go. It’s the same principle as development of varices in cirrhosis.”

“Makes sense,” I said.

“Now let’s talk about ligation of the veins. Idiopathic varicoceles develop because of dilatation of the left testicular vein. Remember, the left testicular vein drains into a high-pressure area? In these varicoceles, there is a retrograde blood flow from the renal down the testicular vein into the Pampiniform plexus. So in patients with idiopathic varicoceles, the testes cannot be draining into the renal vein. In fact, they are draining into the collaterals.”

“So why can’t the testicular vein drain into the collaterals in a tumor?”

“Because the collaterals take long to develop. In an idiopathic varicocele the time span is very long, and good collaterals have developed.”

“Makes sense,” I said, impressed. “Where do these collaterals go?”

“These collaterals connect the testicular veins with some retroperitoneal veins, the inferior epigastric vein, and some others. When you tie off the testicular vein, you block off a high-pressure vein that is retrogradely flowing from the renal towards the testis. This cures the varicocele. And after blocking off the testicular vein, the collaterals happily carry the blood away from the testis!”

“Ahhh, now I get it! In an idiopathic varicocele, the cause is the retrograde flow from the kidney, and the collaterals from the testis have already developed. So you can easily tie off the testicular vein. In a tumor, the cause of the varicocele is the high pressure in the testicular vessels because of inability of the blood to flow into the renal vein. In tumor patients operative ligation of the testicular vein will not help, because the testicular vein is already blocked.”

“True. But if you are going to operate on a patient with a tumor, you may as well remove the tumor.”

“There’s that, too”, I said.

Take home message: The pressure in the renal vein is higher than the pressure in the vena cava, causing varicoceles being commoner on the left than on the right. The high pressure is because of an important law of physics: Poisuille’s law, which states that pressure is inversely proportional to the fourth power of the radius.

 

Reference

Gendel V, Haddadin I, Nosher JL. Antegrade pampiniform plexus venography in recurrent varicocele: Case report and anatomy review. World J Radiol 2011; 3(7): 94-198 Available from: URL: http://www.wjgnet.com/1949-8470/full/v3/i7/ 94.htm DOI: http://dx.doi.org/10.4329/wjr.v3.i7. 94