I find the best way to manipulate XML is with XSLT.
I took a stab at what I thought you were asking for in output, and added some extra records to print out.

!/usr/local/bin/perl -w
use strict;
use warnings;

use XML::LibXML;
use XML::LibXSLT;

my $xml = q{<eSummaryResult>
  <DocSum>
   <Id>25</Id>
   <Item Name="Description" Type="String">Ableson Murine</Item>
  </DocSum>
  <DocSum>
   <Id>26</Id>
   <Item Name="Description" Type="String">yada yada</Item>
  </DocSum>
  <DocSum>
   <Id>27</Id>
   <Item Name="Description" Type="String">yada yada something else</It
+em>
  </DocSum>
</eSummaryResult>
};


my $xslt_stylesheet = q{<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
>
  <xsl:output method="xml" omit-xml-declaration="yes"/>

  <xsl:template match="/eSummaryResult/DocSum"><xsl:apply-templates se
+lect="Id|Item"/></xsl:template>
  <xsl:template match="Id"><xsl:value-of select="."/>, </xsl:template>
  <xsl:template match="Item[@Name='Description']"><xsl:value-of select
+="."/></xsl:template>
</xsl:stylesheet>
};


my $parser      = XML::LibXML->new();
my $xslt        = XML::LibXSLT->new();

my $style_doc   = $parser->parse_string( $xslt_stylesheet );
my $source      = $parser->parse_string( $xml );

my $stylesheet  = $xslt->parse_stylesheet( $style_doc );
my $results     = $stylesheet->transform( $source );

my $output      = $stylesheet->output_string( $results );

print $output;
[download]

Output:

:!./t2.pl

  25, Ableson Murine
  26, yada yada
  27, yada yada something else
[download]

Hope that helps.
Best Regards,
WOnko